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E V Semina

Publications and source records attributed to E V Semina.

At least 19 recordsLinked to original sources
PubMed2004

Zebrafish pitx3 is necessary for normal lens and retinal development.

The human PITX3 gene encodes a bicoid-like homeodomain transcription factor associated with a variety of congenital ocular conditions, including anterior segment dysgenesis, Peter's anomaly, and cataracts. We identified a zebrafish pitx3 gene encoding a protein (Pitx3) that possesses 63% amino acid identity with human PITX3. The zebrafish pitx3 gene encompasses approximately 16.5kb on chromosome 13 and consists of four exons, which is similar to the genomic organization of other pitx genes. Expression of the zebrafish pitx3 gene was studied by in situ mRNA hybridization and RT-PCR. The pitx3 transcripts were detected throughout development with the greatest level of expression occurring in the developing lens and brain at 24hpf. In adults, the highest expression was detected in the eye. Morpholinos were used to knockdown expression of the Pitx3 protein and a control morpholino that contains five mismatched bases was used to confirm the specificity of the phenotypes. The morphants had small eyes, misshapen heads and reduced jaws and fins relative to controls. The morphants exhibited abnormalities in lens development and their retinas contained pyknotic nuclei accompanied by a reduction in the number of cells in different neuronal classes. This suggests the lens is required for retinal development or Pitx3 has an unexpected role in retinal cell differentiation or survival. These results demonstrate zebrafish pitx3 represents a true ortholog of the human PITX3 gene and the general function of the Pitx3 protein in lens development is conserved between mammals and the teleost fish.

Actins↗
PubMed2004

Mutations in PITX2 may contribute to cases of omphalocele and VATER-like syndromes.

Omphalocele is a congenital anomaly with substantial morbidity. Rieger syndrome, an autosomal dominant disorder, is characterized by craniofacial abnormalities and abdominal wall defects. PITX2 mutations are etiologic in >40% of cases of Rieger syndrome. We demonstrate that the birth prevalence of omphalocele is significantly higher in Rieger syndrome than in the general population, with omphaloceles found in 0.03% in the Iowa newborn population and 4.3% of patients with Rieger syndrome. Our objective was to screen coding and conserved non-coding regions of PITX2 for mutations in 209 patients with omphalocele. We identified remarkable evolutionarily conserved regions by comparing the 3'UTR of Pitx2 in 13 vertebrate and 3 invertebrate species. No mutations changing the amino acid sequence were found within the omphalocele population. In one case of omphalocele with VATER-like additional anomalies, a three nucleotide deletion was found in the 3'UTR. This deletion was not seen in 1,186 controls. Also in the 3'UTR, we identified a single nucleotide polymorphism at a highly conserved residue. Our findings suggest additional studies of PITX2 conserved regions will be valuable. We also screened the omphalocele cases for mutations in exon 5 of the gene FLNA. Mutations in FLNA have been shown to cause a broad range of congenital malformations, including otopalatodigital syndrome type 2 in which a missense mutation occurring in exon 5 of FLNA results in omphalocele as part of the phenotype. We did not find any mutations in exon 5 of FLNA in 179 omphalocele cases studied.

Abnormalities, Multiple↗
PubMed2004

Using zebrafish to study the complex genetics of glaucoma.

The overall goal of this review is to highlight the power of zebrafish as a model system for studying complex diseases which involve multiple genetic loci. We are interested in identifying and characterizing genes implicated in the blinding condition of glaucoma. Glaucoma is a complex disease that often involves multiple genetic loci. Most disease causing and modifying genes for glaucoma remain unidentified. However, several genes that regulate various aspects of ocular development have been shown to associate with glaucoma. With zebrafish, forward and reverse genetic approaches can be combined in order to identify critical genetic interactions required for normal and pathological events in the development and maintenance of the eye.

Animals↗
PubMed2001

Identification of a dominant negative homeodomain mutation in Rieger syndrome.

Mutations in the PITX2 bicoid-like homeobox gene cause Rieger syndrome. Rieger syndrome is an autosomal-dominant human disorder characterized by glaucoma as well as dental hypoplasia, mild craniofacial dysmorphism, and umbilical stump abnormalities. PITX2 has also been implicated in the development of multiple organs and left-right asymmetry in the body plan. The PITX2 homeodomain has a lysine at position 50, which has been shown to impart the bicoid-type (TAATCC) DNA binding specificity to other homeodomain proteins. A mutation (K88E), found in a Rieger syndrome patient, changes this lysine to glutamic acid. We were intrigued by the relatively pronounced phenotypic consequences of this K88E mutation. In the initial analyses, the mutant protein appeared to simply be inactive, with essentially no DNA binding and transactivation activities and, unlike the wild type protein, with an inability to synergize with another transcription factor, Pit-1. However, when the K88E DNA was cotransfected with wild type PITX2, analogous to the patient genotype, the K88E mutant suppressed the synergism of wild type PITX2 with Pit-1. In contrast, a different PITX2 homeodomain mutant, T68P, which is also defective in DNA binding, transactivation, and Pit-1 synergism activities, did not suppress the wild type synergism with Pit-1. These results describe the first dominant negative missense mutation in a homeodomain and support a model that may partially explain the phenotypic variation within Rieger syndrome.

Abnormalities, Multiple↗
PubMed2001

Mutations in the human forkhead transcription factor FOXE3 associated with anterior segment ocular dysgenesis and cataracts.

Dysgenesis of the anterior segment of the eye delineates a spectrum of human developmental disorders that show wide phenotypic and genetic heterogeneity. It is also frequently associated with cataracts and glaucoma resulting in visual disability in childhood. The recently described forkhead transcription factor gene Foxe3 was shown to be involved in the dysgenetic lens phenotype in mice, which is characterized by small cataractic lens and anterior segment anomalies. Here we report an identification and characterization of the human ortholog of this gene, FOXE3. The gene was found to be expressed in the anterior lens epithelium and to be mutated in patients with ocular disorders. An insertion of G in the coding region of the FOXE3 gene that occurred 15 nucleotides upstream of the stop codon was identified in a family with anterior segment ocular dysgenesis and cataracts. The mutation causes a frameshift that results in an abnormal sequence of five terminal amino acids and an addition of 111 amino acids to the predicted protein. The mutation was present in two affected individuals from this family and was not identified in 180 normal control chromosomes.

Amino Acid Sequence↗
PubMed2000

Deletion in the promoter region and altered expression of Pitx3 homeobox gene in aphakia mice.

Mouse aphakia (ak) is a recessive phenotype that spontaneously occurs in the 129/Sv-SlJ strain and is characterized by small eyes that lack a lens. We have recently identified a homeobox-containing gene, Pitx3, and have shown that it is expressed in the developing lens and maps to chromosome 19 close to ak in mouse. Human PITX3 gene was found to underlie anterior segment dysgenesis and cataracts. We have now obtained the entire sequence of the mouse Pitx3 gene including 10 kb of the 5' region and 5 kb of the 3' region. Of several microsatellite repeat regions identified within the Pitx3 sequence, one was informative for linkage analysis. No recombination was observed between ak and the Pitx3 marker, indicating that these two loci are closely linked (0.2 +/- 0.2 cM). Additionally, Pitx3 transcripts were not detected in the ak/ak mice either in the lens placode or at later developmental stages of the lens by in situ hybridization. Since no differences were previously found between ak/ak and wild-type sequences in the Pitx3 coding region, we hypothesized that an etiologic mutation is located in the promoter or other regulatory regions. To test this hypothesis we studied the 5' flanking region of the Pitx3 gene. This analysis revealed a deletion of 652 bp located 2.5 kb upstream from the start point of the Pitx3 5' UTR sequence in ak/ak mice. The deletion co-segregated with the ak mutation and was not detected in 16 samples from 10 different mouse strains including the founder strains. Analysis of the 652 bp region identified sequences similar to consensus binding sites for transcription factors AP-2 and Maf that were shown to play a critical role in lens determination. These lines of evidence suggest that the abnormal ocular development in the aphakia mouse is due to the deletion upstream of the Pitx3 gene.

Acetyltransferases↗
PubMed2000

Exclusion of the branchio-oto-renal syndrome locus (EYA1) from patients with branchio-oculo-facial syndrome.

In addition to craniofacial, auricular, ophthalmologic, and oral anomalies, the distinctive phenotype of the branchio-oculo-facial (BOF) syndrome (MIM 113620) includes skin defects in the neck or infra/supra-auricular region. These unusual areas of thin, erythematous wrinkled skin differ from the discrete cervical pits, cysts, and fistulas of the branchio-oto-renal (BOR) syndrome (MIM 113650). Although the BOF and BOR syndromes are sufficiently distinctive that they should not be confused, both can be associated with nasolacrimal duct stenosis, deafness, prehelical pits, malformed pinna, and renal anomalies. Furthermore, a reported father and son [Legius et al., 1990, Clin Genet 37:347-500] had features of both conditions. It was not clear whether they had an atypical presentation of either BOR or BOF syndrome, or represented a private syndrome. In light of these issues, we selected the BOR locus (EYA1) as a possible gene mutation for the BOF syndrome. In five BOF patients, there were no mutations detected in the EYA1 gene, suggesting that it is not allelic to the BOR syndrome.

Branchio-Oto-Renal Syndrome↗
PubMed2000

Antagonistic signals between BMP4 and FGF8 define the expression of Pitx1 and Pitx2 in mouse tooth-forming anlage.

Members of the Pitx/RIEG family of homeodomain-containing transcription factors have been implicated in vertebrate organogenesis. In this study, we examined the expression and regulation of Pitx1 and Pitx2 during mouse tooth development. Pitx1 expression is detected in early development in a widespread pattern, in both epithelium and mesenchyme, covering the tooth-forming region in the mandible, and is then maintained in the dental epithelium from the bud stage to the late bell stage. Pitx2 expression, on the other hand, is restricted to the dental epithelium throughout odontogenesis. Interestingly, from E9.5 to E10.5, the expression domains of Pitx1 and Pitx2, in the developing mandible, overlap with that of Fgf8 but are exclusive to the zone of Bmp4 expression. Bead implantation experiments demonstrate that ectopic expression of Fgf8 can induce/maintain the expression of both Pitx1 and Pitx2 at E9.5. In contrast, Bmp4-expressing tissues and BMP4-soaked beads were able to repress Pitx1 expression in mandibular mesenchyme and Pitx2 expression in the presumptive dental epithelium, respectively. However, the effects of FGF8 and BMP4 are transient. It thus appears that the early expression patterns of Pitx1 and Pitx2 in the developing mandible are regulated by the antagonistic effects of FGF8 and BMP4 such that the Pitx1 and Pitx2 expression patterns are defined. These results indicate that the epithelial-derived signaling molecules are responsible not only for restricting specific gene expression in the dental mesenchyme, but also for defining gene expression in the dental epithelium.

Animals↗
PubMed2000

Isolation and characterization of a novel human paired-like homeodomain-containing transcription factor gene, VSX1, expressed in ocular tissues.

Homeodomain transcription factors control cell fates during the development of all animals. The paired-like subfamily of homeodomain proteins has been particularly implicated in ocular development in different species. In this paper we report the cDNA sequence, genomic structure, localization, and expression data of a novel paired-like homeobox-containing gene, VSX1, isolated from a human embryonic craniofacial cDNA library using the degenerate-PCR approach. The composed VSX1 cDNA sequence of 1433 bp was predicted to encode a protein of 365 amino acid residues. Maximal homology at the protein level was identified with the paired-like homeoproteins of the CVC-domain family: 92-97% identity was seen in the homeodomain region with 55% overall identity to zebrafish and goldfish Vsx1 and 35% overall identity to goldfish Vsx2 and murine Chx10. The gene was found to consist of five exons that are distributed over 6.2 kb of genomic sequence. VSX1 was localized to the 20p11-q11 region, which is homologous with the distal part of mouse chromosome 2. Expression of VSX1 was detected in embryonic craniofacial and adult ocular tissues. Several ocular phenotypes have been mapped to the VSX1 region in both human and mouse genomes, and its candidacy for these disorders is discussed.

Animals↗
PubMed2000

The Pitx2 protein in mouse development.

The Rieger syndrome, an autosomal dominant disorder involving ocular, dental, and umbilical defects is caused by mutations in PITX2, a Bicoid-type homeobox protein. Mouse Pitx2 mRNA is expressed in eye, tooth and umbilicus consistent with the human Riegers phenotype. Moreover, Pitx2 is involved in the Nodal/Sonic hedgehog pathway that determines left/right polarity. In this report we demonstrate a 32-kDa polypeptide on Western blots of nuclear extracts from a rat pituitary cell line, using a Pitx2 specific antibody (designated P2R10). We describe also for the first time expression of the Pitx2 protein in mouse. Pitx2 protein immunostaining was detectable during the development of the eye, tooth, umbilicus, and also in the pituitary, heart, gut, and limb. We demonstrate for the first time directly that Pitx2 is asymmetrically expressed in early heart, gut, and lung development.

Abnormalities, Multiple↗
PubMed2000

Rieger syndrome: a clinical, molecular, and biochemical analysis.

Rieger syndrome (RIEG 1; MIM 180500) is an autosomal dominant disorder of morphogenesis. It is a phenotypically heterogeneous disorder characterized by malformations of the eyes, teeth, and umbilicus. RIEG belongs to the Axenfeld-Rieger group of anomalies, which includes Axenfeld anomaly and Rieger anomaly (or Rieger eye malformation), which display ocular features only. Recently, mutations in the homeodomain transcription factor, PITX2, have been shown to be associated with Rieger syndrome. This review discusses the clinical manifestations of Rieger syndrome and how they correlate with the current molecular and biochemical studies on this human disorder.

Abnormalities, Multiple↗
PubMed1998

Pitx2, a bicoid-type homeobox gene, is involved in a lefty-signaling pathway in determination of left-right asymmetry.

Signaling molecules such as Activin, Sonic hedgehog, Nodal, Lefty, and Vg1 have been found to be involved in determination of left-right (L-R) asymmetry in the chick, mouse, or frog. However, a common signaling pathway has not yet been identified in vertebrates. We report that Pitx2, a bicoid-type homeobox gene expressed asymmetrically in the left lateral plate mesoderm, may be involved in determination of L-R asymmetry in both mouse and chick. Since Pitx2 appears to be downstream of lefty-1 in the mouse pathway, we examined whether mouse Lefty proteins could affect the expression of Pitx2 in the chick. Our results indicate that a common pathway from lefty-1 to Pitx2 likely exists for determination of L-R asymmetry in vertebrates.

Animals↗
PubMed1998

The molecular basis of Rieger syndrome. Analysis of Pitx2 homeodomain protein activities.

Rieger syndrome is an autosomal-dominant developmental disorder that includes glaucoma and mild craniofacial dysmorphism in humans. Mutations in the Pitx2 homeobox gene have been linked to Rieger syndrome. We have characterized wild type and mutant Pitx2 activities using electrophoretic mobility shift assays, protein binding, and transient transfection assays. Pitx2 preferentially binds the bicoid homeodomain binding site and transactivates reporter genes containing this site. The combination of Pitx2 and another homeodomain protein, Pit-1, yielded a synergistic 55-fold activation of the prolactin promoter in transfection assays. Addition of Pit-1 increased Pitx2 binding to the bicoid element in electrophoretic mobility shift assays. Furthermore, we demonstrate specific binding of Pit-1 to Pitx2 in vitro. Thus, wild type Pitx2 DNA binding activity is modulated by protein-protein interactions. We next studied two Rieger mutants. A threonine to proline mutation (T68P) in the second helix of the homeodomain retained DNA binding activity with the same apparent KD and only about a 2-fold reduction in the Bmax. However, this mutant did not transactivate reporter genes containing the bicoid site. The mutant Pitx2 protein binds Pit-1, but there was no detectable synergism on the prolactin promoter. A second mutation (L54Q) in a highly conserved residue in helix 1 of the homeodomain yielded an unstable protein. Our results provide insights into the potential mechanisms underlying the developmental defects in Rieger syndrome.

Amino Acid Sequence↗
PubMed1998

Autosomal dominant iris hypoplasia is caused by a mutation in the Rieger syndrome (RIEG/PITX2) gene.

PURPOSE: To determine whether autosomal dominant iris hypoplasia is caused by mutations in the newly described gene for Rieger syndrome (RIEG/PITX2). METHOD: Mutation screening and sequence analysis was performed in a single family. RESULTS: A novel mutation in the RIEG/PITX2 gene was found in all affected but no unaffected individuals. This mutation would be expected to result in an arginine to tryptophan amino acid change in the homeodomain of solurshin, the RIEG/ITX2 gene product. CONCLUSION: Autosomal dominant iris hypoplasia is caused by a defect in the same gene that is defective in many cases of Rieger syndrome.

Anterior Chamber↗
PubMed1998

A novel homeobox gene PITX3 is mutated in families with autosomal-dominant cataracts and ASMD.

We report here the identification of a new human homeobox gene, PITX3, and its involvement in anterior segment mesenchymal dysgenesis (ASMD) and congenital cataracts in humans. The PITX3 gene is the human homologue of the mouse Pitx3 gene and is a member of the RIEG/PITX homeobox gene family. The protein encoded by PITX3 shows 99% amino-acid identity to the mouse protein, with 100% identity in the homeodomain and approximately 70% overall identity to other members of this family. We mapped the human PITX3 gene to 10q25 using a radiation-hybrid panel. A collection of 80 DNA samples from individuals with various eye anomalies was screened for mutations in the PITX3 gene. We identified two mutations in independent patients. A 17-bp insertion in the 3'-end of the coding sequence, resulting in a frame shift, occurred in a patient with ASMD and cataracts, and a G-->A substitution, changing a codon for serine into a codon for asparagine, in the 5'-end of the gene occurred in a patient with congenital cataracts. Both mutations cosegregate with the disease phenotype in families, and neither were found in up to 300 control individuals studied. Further expression analysis of Pitx3 in the mouse supports a unique role in early ocular development, with later expression extending to the midbrain, tongue, incisors, sternum, vertebrae and limbs. These data strongly suggest a role for PITX3 in ASMD and cataracts and provide new evidence of the contribution of the RIEG/PITX gene family to the developmental program underpinning normal eye formation.

Amino Acid Sequence↗
PubMed1998

Association of MSX1 and TGFB3 with nonsyndromic clefting in humans.

Nonsyndromic cleft lip with or without cleft palate (CL/P) and nonsyndromic cleft palate only (CPO) are common congenital anomalies with significant medical, psychological, social, and economic ramifications. Both CL/P and CPO are examples of complex genetic traits. There exists sufficient evidence to hypothesize that disease loci for CL/P and CPO can be identified by a candidate-gene linkage-disequilibrium (LD) strategy. Candidate genes for clefting, including TGFA, BCL3, DLX2, MSX1, and TGFB3, were screened for LD with either CL/P or CPO in a predominantly Caucasian population, with both case-control- and nuclear-family-based approaches. Previously reported LD for TGFA with both CL/P and CPO could not be confirmed, except in CL/P patients with a positive family history. Also, in contrast to previous studies, no LD was found between BCL3 and either CL/P or CPO. Significant LD was found between CL/P and both MSX1 and TGFB3 and between CPO and MSX1, suggesting that these genes are involved in the pathogenesis of clefting. In addition, a mutation search in the genes DLX2, MSX1, and TGFB3 was performed in 69 CPO patients and in a subset of the CL/P patients. No common mutations were found in the coding regions of these genes; however, several rare variants of MSX1 and TGFB3 were found that may alter the latters' normal function. These results form the basis for future research, including (a) mutation searches in the MSX1 and TGFB3 genes in Caucasian CL/P patients and (b) extension of the search for MSX1 mutations in CPO patients to the noncoding regions.

Amino Acid Substitution↗
PubMed1998

A new human homeobox gene OGI2X is a member of the most conserved homeobox gene family and is expressed during heart development in mouse.

Homeodomain (HD) proteins are transcription regulators controlling a variety of cell fates. The HD region characterizing this protein family is a domain of 60 amino acid residues that recognizes and binds a site in the regulatory region of the target gene. It has been suggested that regions outside the HD may determine the specific functions of the various HD proteins by forming additional contacts with DNA sequences or by interactions with other proteins. We have identified a 14 amino acid motif within the C-terminal region of the protein encoded by the RIEG1 gene that is conserved among several HD proteins. Overlapping expression of the genes encoding these proteins during craniofacial development suggested that they might interact with a common factor. In order to identify additional genes possessing this motif we screened a human craniofacial cDNA library with oligoprobes. A novel gene was identified, exhibiting the most homology to murine Og12x (formerly OG12) and the recently reported human SHOX gene. Human OG12X and murine Og12x are highly homologous and the OG12X and Og12x proteins are 100% identical. In situ hybridization on mouse embryos ranging from 9 to 16 days post-coitum localized murine Og12x mRNA in the heart, otic region, maxillary and mandibular components of the first branchial arch, nasal processes, eyelid, midbrain, medulla oblongata, limbs, dorsal root ganglia and genital tubercle. OG12X was mapped to human chromosome 3q22-26 and murine Og12x to the syntenic region on mouse chromosome 3. Based upon the expression pattern of its mouse cognate, OG12X represents a candidate for the blepharophimosis (BPES) and Cornelia de Lange syndromes previously mapped to this region.

Amino Acid Sequence↗