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PubMed2002

A novel homozygous disruptive mutation in the SRD5A2-gene in a partially virilized patient with 5alpha-reductase deficiency.

Steroid 5alpha-reductase deficiency is a rare autosomal recessive disorder caused by mutations in the SRD5A2-gene, resulting in diminished dihydrotestosterone (DHT) formation and, hence, in a severe virilization deficit of the external genitalia in patients with 46,XY karyotype. The phenotype of affected individuals is variable and has been reported to range from completely female over genital ambiguity to normal male, depending on the type of mutation and its effect on enzyme activity. Here we report an adolescent 46,XY patient with predominantly female appearance, who had been gonadectomized in early infancy. Genital status revealed a urogenital sinus equivalent to Prader stage III. Molecular genetic analysis demonstrated a homozygous point mutation in exon 2 of the SRD5A2-gene, leading to a premature termination in codon position 111 of the 5alpha-reductase 2 enzyme, and not allowing formation of a functional 5alpha-reductase type 2 enzyme. This case demonstrates that even despite a complete loss of function of 5alpha-reductase type 2, marked virilization is possible, most likely the result of a testosterone (T) effect during foetal life.

Adolescent↗

PubMed1996

The CER3 gene of Arabidopsis thaliana is expressed in leaves, stems, roots, flowers and apical meristems.

The eceriferum3 (cer3) locus encodes one of 21 gene products known to be involved in wax biosynthesis in Arabidopsis thaliana. Mutations at these loci are readily identified by their bright, dark-green stems when compared with the more glaucous wild-type plant. Clones of a gene which encodes a 795 amino acid open reading frame have been isolated by using plant DNA flanking the site of a T-DNA insertion in line BRL1. Molecular complementation of the cer3 mutant phenotype by clones of this gene establish that it corresponds to the CER3 gene. Although the 90 kDa predicted amino acid sequence of this gene shows no homology to any other known protein, the second exon of CER3 encodes a RRX12KK nuclear localization sequence (NLS). Southern blot and DNA sequence analysis revealed that the T-DNA is inserted 89 bp downstream of the translation termination codon of this gene. Northern blot hybridization of RNA isolated from the BRL1 mutant with the CER3 cDNA probe indicated that the transcript is absent in this mutant line. Unlike other CER genes that have been cloned to date, high levels of the CER3 transcript were found in all tissues from wild-type plants, that is, leaves, stems, roots, flowers, and apical meristems.

Amino Acid Sequence↗

PubMed2000

Repair of UV damage in plants by nucleotide excision repair: Arabidopsis UVH1 DNA repair gene is a homolog of Saccharomyces cerevisiae Rad1.

To analyze plant mechanisms for resistance to UV radiation, mutants of Arabidopsis that are hypersensitive to UV radiation (designated uvh and uvr) have been isolated. UVR2 and UVR3 products were previously identified as photolyases that remove UV-induced pyrimidine dimers in the presence of visible light. Plants also remove dimers in the absence of light by an as yet unidentified dark repair mechanism and uvh1 mutants are defective in this mechanism. The UVH1 locus was mapped to chromosome 5 and the position of the UVH1 gene was further delineated by Agrobacterium-mediated transformation of the uvh1-1 mutant with cosmids from this location. Cosmid NC23 complemented the UV hypersensitive phenotype and restored dimer removal in the uvh1-1 mutant. The cosmid encodes a protein similar to the S. cerevisiae RAD1 and human XPF products, components of an endonuclease that excises dimers by nucleotide excision repair (NER). The uvh1-1 mutation creates a G to A transition in intron 5 of this gene, resulting in a new 3' splice site and introducing an in-frame termination codon. These results provide evidence that the Arabidopsis UVH1/AtRAD1 product is a subunit of a repair endonuclease. The previous discovery in Lilium longiflorum of a homolog of human ERCC1 protein that comprises the second subunit of the repair endonuclease provides additional evidence for the existence of the repair endonuclease in plants. The UVH1 gene is strongly expressed in flower tissue and also in other tissues, suggesting that the repair endonuclease is widely utilized for repair of DNA damage in plant tissues.

Amino Acid Sequence↗

PubMed1998

Different forms of the mRNA encoding the heat-shock transcription factor are expressed during the life cycle of the parasitic helminth Schistosoma mansoni.

Several cDNAs and a gene encoding the heat-shock transcription factor (HSF) of schistosome were cloned, and multiple forms of the mRNA were found at different developmental stages of the parasite. The encoded protein contained a DNA-binding domain with expected sequence identity (39-58%) to other HSF molecules, and two leucine zipper motifs (LZ123 and LZ4) involved in the oligomerization of HSF. Adult worms express three isoforms of HSF mRNA generated by alternative splicing inside the coding region that contains in-frame splice signals. Introns are not involved in the process since the deleted segments (36 bp or 45 bp) are not flanked by any intron in the gene. Structural variations generated by alternative splicing (insertion of 3 amino acids or 15 amino acids) are continual with LZ4 and added hydrophobic residues are in register with the hydrophobic heptad repeats of LZ4. Structural diversity at the C-terminus of LZ4 may affect the strength of LZ4 interaction with the oligomerization domain (LZ123) and thus modulate the DNA-binding activity of HSF. The conservation of this mechanism in mouse and schistosome may reflect evolutionary pressure to generate multiple HSF species exhibiting functional diversity and capable of responding to different stress signals and physiological signals. Adult worms express HSF mRNA of 2.5 kb, in agreement with the size of the cDNA, while cercariae (developmental stage preceding adult worm) show multiple bands in the range 2.5-3 kb. Available data indicate that the HSF mRNAs of cercariae are inactive. We propose that these mRNA species are generated by an alternative splicing that incorporates introns, which inactivate the mRNA by the insertion of termination codons and/or by shifting of the reading frame. Parasite HSF protein produced in bacteria showed DNA sequence recognition similar to that of HSF in parasite extracts, i.e. the recombinant HSF reacted better with a variant heat-shock element (HSE; one base change in the third NGAAN pentamer of the ideal HSE consensus sequence) than with the ideal HSE. The size of the HSF gene is 12 kb and it is composed of ten exons and nine introns. Excluding the introns, the gene and cDNA show 100% sequence identity. A plant HSF gene contains only a single intron, which matches with the position of intron I2 of schistosome. That the position of this intron is conserved in remote species is indicative of an important function during evolution of the HSF gene.

Alternative Splicing↗

PubMed1998

Novel homozygous and compound heterozygous COL17A1 mutations associated with junctional epidermolysis bullosa.

Junctional epidermolysis bullosa is a heritable, heterogeneous blistering skin disease with mechanically induced dermal-epidermal separation, mild skin atrophy, nail dystrophy, and alopecia. Four unrelated junctional epidermolysis bullosa families with different phenotypes were investigated here and four novel mutations associated with the disease were identified. Patients 1, 2, and 3 had generalized atrophic benign epidermolysis bullosa, with nonscarring blistering and varying degree of alopecia. Patient 4 had the localisata variant of junctional epidermolysis bullosa, with predominantly acral blistering and normal hair. All patients had mutations in the COL17A1 gene encoding collagen XVII, a hemidesmosomal transmembrane protein. Patients 1 and 2 carried homozygous deletions 520delAG and 2965delG, respectively. Patient 3 was compound heterozygous for a missense and a deletion mutation (G539E and 2666delTT), and patient 4 was heterozygous for a known mutation R1226X. The deletions led to premature termination codons and to drastically reduced collagen XVII mRNA and protein levels, consistent with the absence of the collagen in generalized atrophic benign epidermolysis bullosa skin. The missense mutation G539E allowed synthesis of immunoreactive collagen XVII in keratinocytes, but prevented its secretion, thus causing lack of the protein in the skin. The data suggest that different COL17A1 mutations and their combinations can result in a spectrum of biologic and clinical phenotypes of not only generalized atrophic benign epidermolysis bullosa, but also localized junctional epidermolysis bullosa.

Aged↗

PubMed1999

A novel point mutation affecting the tyrosine kinase domain of the TRKA gene in a family with congenital insensitivity to pain with anhidrosis.

A nerve growth factor receptor encoded by the TRKA gene plays an important part in the formation of autonomic neurons and small sensory neurons in dorsal root ganglia and in signal transduction through its intracytoplasmic tyrosine kinase domain. Recently, three mutations in the tyrosine kinase domain of TRKA have been reported in patients with congenital insensitivity to pain with anhidrosis, which is an autosomal recessive disorder characterized by recurrent fever due to absence of sweating, no reaction to noxious stimuli, self-mutilating behavior, and mental retardation. We examined the TRKA gene in five generations of a large Japanese family with many consanguineous marriages who live in a small remote island of the southern part of Japan. We found a novel point mutation at nucleotide 1825 (A-->G transition) resulting in Met-581-Val in the tyrosine kinase domain. Two of the three affected patients were homozygous for this mutation; however, the third affected patient was heterozygous. Further analysis revealed that the third patient was a compound heterozygote with the Met-581-Val mutation in one allele and with a single base C deletion mutation at nucleotide 1726 in exon 14 in the other allele, resulting in a frameshift and premature termination codon.

Adult↗

PubMed1999

Compound heterozygosity for novel splice site mutations in the BPAG2/COL17A1 gene underlies generalized atrophic benign epidermolysis bullosa.

Generalized atrophic benign epidermolysis bullosa, GABEB (OMIM# 226650), is a nonlethal variant of epidermolysis bullosa with autosomal recessive inheritance pattern. The pathogenesis of this disorder can be caused by mutations affecting two different gene/protein systems. Most of the mutations have been identified in the BPAG2/COL17A1 gene encoding a hemidesmosomal transmembrane protein, the 180 kDa bullous pemphigoid antigen (BP180), also known as type XVII collagen. The minority of the mutations are localized in the LAMB3 gene encoding the beta3 polypeptide of laminin 5. In In this study we describe a GABEB patient who showed absent expression of BP180 in the cultured keratinocytes as well as in the skin. The patient was a compound heterozygote for two different splice site mutations, 3053-1G-->C and 3871+1G-->C, affecting the extra-cellular domain of the protein. These mutations resulted in multiple aberrant splice variants, three of them causing premature termination codons for translation. This case, dealing with out-of-frame splice site mutations in BPAG2/COL17A1, attests to the molecular heterogeneity of GABEB.

Adult↗

PubMed2002

Netherton syndrome: disease expression and spectrum of SPINK5 mutations in 21 families.

Netherton syndrome is a severe autosomal recessive skin disorder characterized by congenital erythroderma, a specific hair-shaft abnormality, and atopic manifestations with high IgE levels. Recently, we identified SPINK5, which encodes the serine protease inhibitor Kazal-type 5 protein (LEKTI), as the defective gene in Netherton syndrome. Here we describe the intron-exon organization of the gene and characterize the SPINK5 mutations in patients from 21 families of different geographic origin, using denaturing high performance liquid chromatography and direct sequencing. We identified 18 mutations, of which 13 were novel and seven (39%) were recurrent. The majority of the mutations were clustered between exons 1-8 and exons 21-26. They comprised four nonsense mutations (22%), eight frameshift insertions or deletions (44%), and six splice-site defects (33%). All mutations predict the formation of premature termination codons. Northern blot analysis showed variable reduction of SPINK5 mutant transcript levels, suggesting variable efficiency of nonsense-mediated mRNA decay. Seven patients were homozygotes, eight were compound heterozygotes, and five were heterozygotes with only one identifiable SPINK5 mutation. Five mutations, one of which resulted in perinatal lethal disease in three families, were associated with certain ethnic groups. We also describe 45 intragenic polymorphisms in the patients studied. The clinical features of erythroderma, trichorrhexis invaginata, and atopic manifestations were present in the majority of affected individuals and ichthyosis linearis circumflexa was seen in 12 out of 24 patients. Interfamilial and intrafamilial variation in disease severity was observed, with no clear correlation between mutations and phenotype, suggesting that the degree of severity may be affected by other factors.

Adolescent↗

PubMed2002

Partial revertant mosaicism of keratin 14 in a patient with recessive epidermolysis bullosa simplex.

A patient with recessive epidermolysis bullosa simplex due to a previously described homozygous KRT14 1842-2A-->C splice-site mutation was re-examined, because we unexpectedly found signs of revertant mosaicism. The germline mutation resulted in different aberrant transcripts containing premature termination codons, all leading to truncated keratin 14 proteins. Basal keratinocytes in skin and in culture completely lacked keratin 14 and intermediate filaments. From this keratin 14-/- patient we started cultures from a new skin biopsy and here, we serendipitously found keratinocytes that spontaneously expressed keratin 14. This biopsy had been taken from an area of skin that was clinically affected, because blisters could simply be evoked by gentle rubbing. Immunofluorescence and electron microscopy of additional biopsies from this skin area revealed a mosaic expression of keratin 14 and reappearance of intermediate filaments in basal keratinocytes. Immunoblotting showed a revertant keratin 14 polypeptide with seemingly normal molecular weight. DNA analysis of exon 2 and its flanking intron borders showed no additional mutations in the genomic KRT14 sequence. Analysis of mRNA isolated from mosaic skin keratinocytes revealed an additional in-frame transcript (1844T-->G, 1845Delta6) that codes for an abnormal keratin 14 polypeptide with a two residue deletion and one amino acid change. The re-expression of a revertant, albeit abnormal, keratin 14 polypeptide, so-called partial revertant mosaicism, accounts for the antibody staining pattern and for the reappearance of intermediate filaments, which however, are semifunctional and not able to revert the clinical phenotype. The combination of a keratin 14-positive and a keratin 14-negative cell population in epidermis as well as in cultured keratinocytes suggests that the cellular reversion might be caused by an endogenous factor. We hypothesize that a second somatic modulating factor in the genome that affects the processing of the mutant KRT14 pre-mRNA may underlie this phenomenon.

Aged↗

PubMed2002

Animal models for skin blistering conditions: absence of laminin 5 causes hereditary junctional mechanobullous disease in the Belgian horse.

Recent achievements in the genetic correction of keratinocytes isolated from patients with junctional epidermolysis bullosa have paved the way to a gene therapy approach for the disease. Because gene therapy protocols require preclinical validation in animals, we have characterized spontaneous animal models of junctional epidermolysis bullosa. In this study we have elucidated the genetic basis of the hereditary junctional mechanobullous disease in the Belgian horse, a condition characterized by blistering of the skin and mouth epithelia, and exungulation (loss of the hoof). Immunofluorescence analysis associated the condition to the absent expression of the gamma2 chain of laminin 5 and designated Lamc2 as the candidate gene. Comparative analysis of the nucleotide sequence of the full-length gamma2 cDNA isolated by reverse transcription polymerase chain reaction amplification of total RNA purified from the epithelium of a junctional epidermolysis bullosa foal and a healthy control disclosed a homozygous basepair insertion (1368insC) in the affected animal. Mutation 1368insC results in a downstream premature termination codon and is predicted to cause absent expression of the laminin gamma2 polypeptide. Our results also show that: (i) the horse junctional epidermolysis bullosa genetically corresponds to the severe Herlitz form of junctional epidermolysis bullosa in man; (ii) the amino acid sequence and structure of the horse laminin gamma2 chain are virtually identical to the human counterpart; (iii) the moderate eruption of skin blisters in the affected animals with respect to the human Herlitz junctional epidermolysis bullosa patients correlates with the protection provided by hair. Our observations suggest that the affected foals are a convenient source of epithelial cells from tissues that cannot be obtained from human junctional epidermolysis bullosa patients, and imply that hairless strains of animals with recessive skin disorders would be the best models for in vivo gene therapy approaches to skin blistering diseases.

Animals↗

PubMed2002

Loss of cell adhesion in Dsg3bal-Pas mice with homozygous deletion mutation (2079del14) in the desmoglein 3 gene.

Pemphigus encompasses a group of autoimmune blistering diseases with circulating pathogenic autoantibodies recognizing several proteins, including the desmosomal cadherin, desmoglein 3. Targeted disruption of the Dsg3 gene by homologous recombination (Dsg3tm1stan) in mouse results in fragility of the skin and oral mucous membranes, analogous to the human disease. In addition, the Dsg3tm1stan mice develop phenotypic runting and hair loss, identical to that of the mouse mutant, Dsg3bal-2J. The Dsg3bal-2J mice are homozygous for a 1 bp insertion (2275insT) in the Dsg3 gene resulting in a nonfunctional Dsg3 mRNA. In this study, we characterized an allelic mutation, Dsg3bal-Pas, with clinical features similar to those in Dsg3bal-2J. We have identified a 14 bp deletion in exon 13 of the Dsg3 gene resulting in a frameshift and premature termination codon 7 bp downstream from the site of the deletion and causing a truncation of the desmoglein 3 polypeptide by 199 amino acids, eliminating virtually all of the intracellular domain. We demonstrate that, although a Dsg3 mRNA transcript was detectable in Dsg3bal-Pas skin, the corresponding protein for desmoglein 3 was completely absent in the oral mucosal epithelium of homozygous Dsg3bal-Pas compared with that of +/Dsg3bal-Pas mice. No significant changes in the expression of desmogleins 1 and 2 were detected. To elucidate a potential mechanism causing loss of cell adhesion in the Dsg3bal-Pas mice, we generated a myc-tagged truncated Dsg3bal-Pas desmoglein 3 protein and expressed it in keratinocytes. The myc-tagged truncated Dsg3bal-Pas desmoglein 3 protein was found predominantly in the cytoplasm possibly due to increased proteolytic degradation. Cell surface staining was also detected but was jagged, not linear along the cell-cell border like that observed for the full-length desmoglein 3. The expression of the myc-tagged truncated Dsg3bal-Pas desmoglein 3 protein resulted in a reduction in staining of other desmosomal proteins, including desmoglein 1 and 2, plakophilin 2, and plakoglobin. In addition, the cells expressing myc-tagged truncated Dsg3bal-Pas desmoglein 3 protein underwent dramatic changes in cell morphology and exhibited striking extensive filopodia. Collectively, these data showed that the perturbation of desmoglein 3 found in the Dsg3bal-Pas mice resulted in disadhesion of keratinocytes manifested with blistering phenotype.

Alopecia↗

PubMed2003

Novel SLC39A4 mutations in acrodermatitis enteropathica.

Acrodermatitis enteropathica is an autosomal recessive disease characterized by skin involvement due to defective intestinal zinc absorption. Usually, the skin lesions include erythema, erosions, and small blisters in perioral, perianal regions, and hands and feet, which develop soon after weaning from the breast. The acrodermatitis enteropathica gene has been localized to chromosomal region 8q24.3 and subsequently the SLC39A4 gene has been disclosed as the acrodermatitis enteropathica gene. SLC39A4 mutations have been demonstrated in several acrodermatitis enteropathica families, and in this study we have examined two Japanese acrodermatitis enteropathica families for SLC39A4 mutations. The mutation detection strategy consisted of polymerase chain reaction amplification of all 12 exons and flanking intronic sequences, followed by direct nucleotide sequencing. It revealed three novel mutations, 1017ins53, which creates a premature termination codon, and two mis-sense mutations, R95C and Q303H.

Absorption↗

PubMed2003

Mutations in the sarcoplasmic/endoplasmic reticulum Ca2+ ATPase isoform cause Darier's disease.

Darier's disease is an autosomal dominantly inherited skin disorder, characterized by loss of adhesion between epidermal cells and abnormal keratinization. ATP2A2 encoding the sarcoplasmic/endoplasmic reticulum Ca2+ ATPase (SERCA)2 has been identified as the defective gene in Darier's disease. All mutations previously reported occur in the region of ATP2A2 encoding both SERCA2a and SERCA2b isoforms. These isoforms result from alternative splicing of exon 20, with SERCA2b being the major isoform expressed in the epidermis. In this report, we studied a family affected with Darier's disease and identified a deletion (2993delTG) in a region of exon 20 of ATP2A2, which is specific for SERCA2b. This heterozygous mutation predicts a frameshift with a premature termination codon (PTC+32aa) in the eleventh transmembrane domain of SERCA2b. It segregates with the disease phenotype in the family members tested, and functional analysis shows a drastic reduction of the expression of the mutated protein in comparison with the wild-type SERCA2b. Our result suggests that the mutated allele causes the disease phenotype through loss of function of SERCA2b isoform. This finding indicates that SERCA2b plays a key role in the biology of the epidermis, and its defects are sufficient to cause Darier's disease.

Animals↗

PubMed2003

Frameshift mutation of the zinc finger homeo box 1 B gene in syndromic corpus callosum agenesis (Mowat-Wilson syndrome).

We report a girl who had Hirschsprung disease in association with distinct facial appearance, microcephaly, agenesis of the corpus callosum and mental retardation (Mowat-Wilson syndrome). Mutation analysis of the zinc finger homeo box 1 B (ZFHX1 B) gene revealed a de novo 7 bp deletion (TGGCCCC) at nucleotide 1773 (1773 delTGGCCCC) resulting in a frameshift and leading to a termination codon at amino acid residue 604 (604 X) in exon 8 C. The zinc finger homeo box 1 B (Smad interacting protein-1) is a transcription corepressor of Smad target genes with functions in the patterning of neural crest derived cells, CNS, and midline structures. Mutations in ZFHX1 B can lead to neurological disorders in addition to dysmorphic features, megacolon, and other malformations.

Abnormalities, Multiple↗

PubMed2006

Three novel point mutations of the CYP21 gene detected in classical forms of congenital adrenal hyperplasia due to 21-hydroxylase deficiency.

Congenital adrenal hyperplasia (CAH) [OMIM 201 910] is a group of autosomal recessive disorders most commonly due to 21-hydroxylase deficiency and presenting with a wide range of clinical manifestations. A limited number of inactivating pseudogene-derived mutations account for the majority of 21-hydroxylase gene ( CYP21) mutations, additional rare mutations can be found in single families and small populations. We found three novel CYP21 mutations in CAH patients suffering from the classical form of the disease, of which one is a frameshift mutation (1353-1354insA) leading to a premature termination codon (K277K, Q228A...E294X), one results in a premature stop codon (2551C>T, R444X), and one is a missense mutation (2609T>C; P463L). The frameshift and premature stop mutations can be predicted to result in a CYP21 protein without any residual enzyme activity. To determine the functional consequences of the P463L mutation, the IN VITRO enzyme activity was studied in COS-7 cells and revealed a reduced 21-hydroxylase activity of 2.6+/-0.8 (SD)% for the conversion of 17-hydroxyprogesterone (17OHP) to 11-deoxycortisol and of 3.0+/-0.5 % for the conversion of progesterone to 11-deoxycorticosterone (DOC). We conclude that functional analyses of unknown mutations provide information on the disease severity and should be always performed when novel CYP21 mutations are detected. Knowledge of the residual 21-hydroxylase function improves both genetic counselling and individual clinical management in CAH patients.

Adrenal Hyperplasia, Congenital↗

PubMed1995

Mutations of the growth hormone receptor in children with idiopathic short stature. The Growth Hormone Insensitivity Study Group.

BACKGROUND: Short stature in children who are not deficient in growth hormone (GH) is probably caused by a variety of defects. Some children with idiopathic short stature have low serum concentrations of GH-binding protein, which is derived from the GH receptor. The possibility that low serum concentrations of GH-binding protein might indicate partial insensitivity to GH led us to investigate possible defects in the gene for the GH receptor in children with idiopathic short stature and low serum concentrations of GH-binding protein. METHODS: We studied 14 children with idiopathic short stature who were selected on the basis of normal GH secretion and low serum concentrations of GH-binding protein. Analysis of single-strand conformation polymorphisms and DNA sequencing were both used to identify mutations in the GH-receptor gene. RESULTS: Mutations in the region of the GH-receptor gene that codes for the extracellular domain of the receptor were found in 4 of the 14 children, but in none of 24 normal subjects. One of the four children with mutations was a compound heterozygote, with one mutation that reduced the affinity of the receptor for GH and a second mutation that may affect a function other than ligand binding. The remaining three children had single mutations in one allele of the gene. One mutation introduced a premature termination codon, and two caused substitutions of single amino acids in a structurally conserved domain of the receptor. CONCLUSIONS: Some children with idiopathic short stature may have partial insensitivity to GH due to mutations in the GH-receptor gene.

Adolescent↗

PubMed1997

The follicle-stimulating hormone beta-subunit gene of the common brushtail possum (Trichosurus vulpecula): analysis of cDNA sequence and expression.

Reverse transcription-PCR has been used to obtain a cDNA sequence from the follicle-stimulating hormone (FSH) beta-subunit gene of the Australian brushtail possum (Trichosurus vulpecula). Comparisons of the possum FSHbeta-mRNA coding region nucleotide sequence with that of six eutherian mammal homologues reveals a mean percent identity of 77.3% and 76.8% at the nucleotide and predicted amino acid-sequence levels respectively. Furthermore, the predicted amino acid sequence of the possum FSHbeta mature protein shows evolutionary conservation of twelve cysteine residues and two potential N-linked glycosylation sites. The protein lacks the CAGY motif present in most reported glycoprotein beta-subunit sequences. The translation termination codon and consensus polyadenylation sequence overlap, a feature observed in other mammalian FSHbeta genes. Northern hybridization of total RNA from adult female possum pituitary revealed three hybridizing transcripts of approximately 2.8, 1.2 and 0.5 kb which may arise from utilizing alternative polyadenylation signals. In situ hybridization localized the FSHbeta transcripts to a sub-population of anterior pituitary cells interpreted as being gonadotropes. In summary the results indicate considerable evolutionary conservation of the structure of the FSH beta-subunit gene between the marsupial and eutherian mammalian lineages.

Adult↗

PubMed2004

A nuclear translation-like factor eIF4AIII is recruited to the mRNA during splicing and functions in nonsense-mediated decay.

In eukaryotes, a surveillance mechanism known as nonsense-mediated decay (NMD) degrades the mRNA when a premature-termination codon (PTC) is present. NMD requires translation to read the frame of the mRNA and detect the PTC. During pre-mRNA splicing, the exon-exon junction complex (EJC) is recruited to a region 20-24 nt upstream of the exon junction on the mature mRNA. The presence of a PTC upstream from the EJC elicits NMD. Eukaryotic initiation factor 4A (eIF4A) III is a nuclear protein that interacts physically or functionally with translation initiation factors eIF4G and eIF4B, respectively, and shares strikingly high identity with the initiation factors eIF4AI/II. Here we show that siRNA against eIF4AIII, but not against eIF4AI/II, inhibits NMD. Moreover, eIF4AIII, but not eIF4AI, is specifically recruited to the EJC during splicing. The observations that eIF4AIII is loaded onto the mRNA during splicing in the nucleus, has properties related to a translation initiation factor, and functions in NMD raises the possibility that eIF4AIII substitutes for eIF4AI/II during NMD.

Animals↗