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Biomedical subjects

Radha Ayyagari

Publications and source records attributed to Radha Ayyagari.

At least 19 recordsLinked to original sources
PubMed2007

Loss of functional ELOVL4 depletes very long-chain fatty acids (> or =C28) and the unique omega-O-acylceramides in skin leading to neonatal death.

Mutations in elongation of very long-chain fatty acid-4 (ELOVL4) are associated with autosomal dominant Stargardt-like macular degeneration (STGD3), with a five base-pair (5 bp) deletion mutation resulting in the loss of 51 carboxy-terminal amino acids and truncation of the protein. In addition to the retina, Elovl4 is expressed in a limited number of mammalian tissues, including skin, with unknown function(s). We generated a knock-in mouse model with the 5-bp deletion in the Elovl4 gene. As anticipated, mice carrying this mutation in the heterozygous state (Elovl4(+/del)) exhibit progressive photoreceptor degeneration. Unexpectedly, homozygous mice (Elovl4(del/del)) display scaly, wrinkled skin, have severely compromised epidermal permeability barrier function, and die within a few hours after birth. Histopathological evaluation of the Elovl4(del/del) pups revealed no apparent abnormality(ies) in vital internal organs. However, skin histology showed an abnormally-compacted outer epidermis [stratum corneum (SC)], while electron microscopy revealed deficient epidermal lamellar body contents, and lack of normal SC lamellar membranes that are essential for permeability barrier function. Lipid analyses of epidermis from Elovl4(del/del) mice revealed a global decrease in very long-chain fatty acids (VLFAs) (i.e., carbon chain > or =C28) in both the ceramide/glucosylceramide and the free fatty-acid fractions. Strikingly, Elovl4(del/del) skin was devoid of the epidermal-unique omega-O-acylceramides, that are key hydrophobic components of the extracellular lamellar membranes in mammalian SC. These findings demonstrate that ELOVL4 is required for generating VLFA critical for epidermal barrier function, and that the lack of epidermal omega-O-acylceramides is incompatible with survival in a desiccating environment.

Animals↗
PubMed2006

An unusual X-linked retinoschisis phenotype and biochemical characterization of the W112C RS1 mutation.

A 52-year-old subject harboring an RS1 gene W112C mutation presented with a prominent and asymmetric tapetal-like retinal sheen. Transient ERG responses were smaller and slower in the eye with the more extensive sheen, an association that, to our knowledge, had not been previously reported. An ON-pathway dysfunction explained the abnormalities of the transient but not those of the flicker ERGs. Although in vitro studies showed that the W112C mutant retinoschisin is present only in the cellular fraction and is not secreted, disease expression was remarkably mild, consistent with the notion of the existence of genetic and/or epigenetic disease modifiers.

Cells, Cultured↗
PubMed2006

Haploinsufficiency is not the key mechanism of pathogenesis in a heterozygous Elovl4 knockout mouse model of STGD3 disease.

PURPOSE: Autosomal dominant Stargardt-like (STGD3) disease results from mutations in the ELOVL4 gene (elongation of very-long-chain fatty acids). This study was undertaken to characterize a mouse model with a targeted deletion of Elovl4 and to explore the role of this gene in retinal/macular degeneration. METHODS: A construct targeted to exon 2 of the Elovl4 gene was used to suppress expression of the gene. Elovl4 homozygous pups were nonviable and were not available for study. Hence, the analysis was performed on heterozygous Elovl4(+/-) mice 16 to 22 month of age and littermate wild-type (WT) control mice of the same age. Characterization included examining gene message and protein levels, electroretinogram (ERG), retinal morphology and ultrastructure, and plasma and retinal fatty acid composition. RESULTS: Although the level of Elovl4 mRNA was reduced in Elovl4(+/-) retinas, only minimal morphologic abnormalities were found, and the retinal (ERG) function was essentially normal in Elovl4(+/-) retinas compared with the WT control retinas. Systemic fatty acid profiles of Elovl4(+/-) mice were unremarkable, although the concentration of several fatty acids was significantly lower in Elovl4(+/-) retinas, particularly the monounsaturated fatty acids. CONCLUSIONS: The detailed characterization of this animal model provides the first in vivo evidence that Elovl4 haploinsufficiency is not the underlying key disease mechanism in STGD3. The results are consistent with a dominant negative mechanism for the deletion mutation. The Elovl4 knockout mouse is one of three complementary animal models that will help elucidate the disease mechanism.

Animals↗
PubMed2006

Complement factor H: spatial and temporal expression and localization in the eye.

PURPOSE: Complement factor H (CFH) is a component of the mammalian complement system, which regulates the alternative pathway of complement activation and protects the host cell from inappropriate complement activation. CFH is a key regulator of innate immunity, and CFH deficiency leads to membranoproliferative glomerulonephritis type II. A variation in human CFH, Y402H, has been shown to be associated with an increased risk for age-related macular degeneration. The authors describe studies on the spatial and temporal expression of the CFH gene and localization of this protein in ocular tissues to gain insight into its role in the eye. METHODS: CFH expression in human and mouse tissues was studied by quantitative RT-PCR and Western blot analysis, and localization of CFH was studied by immunohistochemical analysis followed by fluorescence microscopy. RESULTS: In human and mouse, CFH expression was found to be similar to the highest level of expression in the liver. In ocular tissue, CFH was detected in the distalmost optic nerve (3 mm) cut from the scleral surface of the eyeball, sclera, RPE-choroid, retina, lens, and ciliary body. In mouse, Cfh expression was observed from early embryonic stages, and in the eye its expression increased with age. CONCLUSIONS: A significant level of CFH expression is maintained in different ocular tissues during development and aging. Sustained high levels of CFH expression in eye tissues suggest that this protein may play a role in protecting these tissues from indiscriminate complement activation and inflammatory insult.

Aged↗
PubMed2006

CTRP5 is a membrane-associated and secretory protein in the RPE and ciliary body and the S163R mutation of CTRP5 impairs its secretion.

PURPOSE: In a prior study, a S163R mutation in the complement-1q tumor necrosis factor-related protein 5 (CTRP5/ C1QTNF5) was reported to be associated with early-onset long anterior zonules (LAZ) and late-onset retinal degeneration (L-ORD). The ocular tissues involved in the phenotype are the retinal pigment epithelium (RPE) in the posterior segment and ciliary epithelium (CE) and lens in the anterior segment. The purpose of this study was to characterize the spatial and temporal expression of the mouse Ctrp5 gene, determine tissue and subcellular localization, and study the effect of the S163R mutation. METHODS: The expression of the Ctrp5 gene in the mouse was studied by quantitative (q)RT-PCR and in situ hybridization. CTRP5 protein expression and distribution were studied by Western blot analysis, immunohistochemistry, and immunoelectron microscopy. Cellular location of wild-type and mutant CTRP5 in MDCK and COS-7 cells was determined by immunofluorescence and immunoblot analysis. RESULTS: A significant level of Ctrp5 expression was detected in the adult mouse in the ciliary body (CB) and RPE, and expression started at a very early stage of embryogenesis. Immunohistochemical analysis showed CTRP5 protein in the apical processes of the RPE and forming a hexagonal lattice associated with the RPE lateral membranes. In the ciliary body, CTRP5 was localized to the apical aspects of the CE, the region between the bilayered ciliary epithelial cells. The membrane association of CTRP5 in the RPE and CE was further confirmed by immunoelectron microscopy. Furthermore, cultured cells were used to show that the CTRP5 is a secretory protein and that its secretion is impaired by the S163R mutation. CONCLUSIONS: CTRP5, a secretory and membrane-associated protein, is localized to the lateral and apical membranes of the RPE and CB. Impaired secretion of the mutant protein may underlie the pathophysiology of L-ORD and LAZ.

Animals↗
PubMed2006

Elovl4 5-bp-deletion knock-in mice develop progressive photoreceptor degeneration.

PURPOSE: To develop and characterize a heterozygous knock-in mouse model carrying the 5-bp deletion in Elovl4 (E_mut+/-) and to study the pathology underlying Stargardt-like macular degeneration (STGD3). METHODS: E_mut+/- mice were generated by targeting a 5-bp deletion (AACTT) in the Elovl4 gene by homologous recombination. E_mut+/- mice of age 2 to 18 months and age-matched wild-type (Wt) littermate control animals were analyzed for the expression of Elovl4 transcript, ELOVL4 protein, photoreceptor-specific genes, and retinal fatty acid composition. Functional retinal changes were evaluated by electroretinography (ERG) and by morphologic and ultrastructural criteria. RESULTS: E_mut+/- mice retinas showed the presence of both Wt and mutant Elovl4 transcripts and proteins. Morphologic evaluation revealed cone photoreceptor ultrastructural abnormalities as early as 2 months of age, accumulation of lipofuscin in retinal pigment epithelium (RPE), and subretinal deposits at later ages. Shortening of rod outer segments (OS) was observed at approximately 10 months of age. Both cone and rod changes progressed with age. Unlike rod-specific genes, expression of selected cone specific genes was significantly reduced by 7 months of age. Mixed rod-cone and light-adapted b-waves were higher than normal at both 8 and 15 months. Levels of the fatty acids 20:5 (P = 0.027), 22:5 (P = 0.040) and 24:6 (P = 0.005) were found to be significantly lower in the retinas of E_mut+/- mice than in retinas of control subjects. CONCLUSIONS: E_mut+/- animals display characteristic features associated with Stargardt-like macular degeneration and serve as a model for the study of the mechanism underlying STGD3.

Animals↗
PubMed2006

Spatial and temporal expression of MFRP and its interaction with CTRP5.

PURPOSE: Mutations in the membrane frizzled-related protein (MFRP) gene cause nanophthalmos in humans, and a splice site mutation causes recessive retinal degeneration in the rd6 mouse. In human and mouse genomes, the MFRP gene lies adjoining to the complement 1q tumor necrosis factor-related protein 5 (CTRP5/C1QTNF5) gene involved in causing retinal degeneration and abnormal lens zonules in human. The purpose of this study was to characterize the spatial and temporal expression of the mouse Mfrp gene, determine tissue and subcellular localization of MFRP protein, and study its interaction with CTRP5. METHODS: Expression of the Mfrp gene in the mouse was studied by quantitative (q)RT-PCR. MFRP protein expression and distribution were studied by Western blot analysis, immunohistochemistry, and immunoelectron microscopy. Interaction with CTRP5 was studied by immunoprecipitation and immunoblot analysis, using mouse eye and human retinal pigmented epithelium (RPE) choroid extracts and by expressing full-length CTRP5 and MFRP in a heterologous system. RESULTS: The Mfrp gene is specifically expressed in RPE and ciliary body (CB), and its expression starts during early stages of embryogenesis. In the albino mouse eye, MFRP is localized to the apical and basal membranes of RPE and ciliary epithelium (CE). In addition, MFRP and CTRP5 were found to colocalize in RPE, CE, and MDCK cells, a general model of polarized epithelia. These proteins interact with each other in ocular tissues and also in a heterologous system. CONCLUSIONS: MFRP is localized to the plasma membrane of CE and RPE, and colocalizes and interacts with CTRP5 indicating a functional relationship between these two proteins.

Animals↗
PubMed2005

Severe autosomal recessive retinitis pigmentosa maps to chromosome 1p13.3-p21.2 between D1S2896 and D1S457 but outside ABCA4.

A severe form of autosomal recessive retinitis pigmentosa (arRP) was identified in a large Pakistani family ascertained in the Punjab province of Pakistan. All affected individuals in the family had night blindness in early childhood, early complete loss of useful vision, and typical RP fundus changes plus macular degeneration. After exclusion of known arRP loci, a genome-wide scan was performed using microsatellite markers at about 10 cM intervals and calculating two-point lod scores. PCR cycle dideoxynucleotide sequencing was used to sequence candidate genes inside the linked region for mutations. RP in this family shows linkage to markers in a 10.5 cM (8.9 Mbp) region of chromosome 1p13.3-p21.2 between D1S2896 and D1S457. D1S485 yields the highest lod score of 6.54 at theta=0. Sequencing the exons and intron-exon boundaries of five candidate genes and six ESTs in this region, OLFM3, GNAI3, LOC126987, FLJ25070, DKFZp586G0123, AV729694, BU662869, BU656110, BU171991, BQ953690, and CA397743, did not identify any causative mutations. This novel locus lies approximately 4.9 cM (7.1 Mbp) from ABCA4, which is excluded from the linked region. Identification and study of this gene may help to elucidate the phenotypic diversity of arRP mapping to this region.

Adolescent↗
PubMed2005

Mutations in TCF8 cause posterior polymorphous corneal dystrophy and ectopic expression of COL4A3 by corneal endothelial cells.

Posterior polymorphous corneal dystrophy (PPCD, also known as PPMD) is a rare disease involving metaplasia and overgrowth of corneal endothelial cells. In patients with PPCD, these cells manifest in an epithelial morphology and gene expression pattern, produce an aberrant basement membrane, and, sometimes, spread over the iris and nearby structures in a way that increases the risk for glaucoma. We previously mapped PPCD to a region (PPCD3) on chromosome 10 containing the gene that encodes the two-handed zinc-finger homeodomain transcription factor TCF8. Here, we report a heterozygous frameshift mutation in TCF8 that segregates with PPCD in the family used to map PPCD3 and four different heterozygous nonsense and frameshift mutations in TCF8 in four other PPCD probands. Family reports of inguinal hernia, hydrocele, and possible bone anomalies in affected individuals suggest that individuals with TCF8 mutations should be examined for nonocular anomalies. We detect transcripts of all three identified PPCD genes (VSX1, COL8A2, and TCF8) in the cornea. We show presence of a complex (core plus secondary) binding site for TCF8 in the promoter of Alport syndrome gene COL4A3, which encodes collagen type IV alpha 3, and we present immunohistochemical evidence of ectopic expression of COL4A3 in corneal endothelium of the proband of the original PPCD3 family. Identification of TCF8 as the PPCD3 gene provides a valuable tool for the study of critical gene regulation events in PPCD pathology and suggests a possible role for TCF8 mutations in altered structure and function of cells lining body cavities other than the anterior chamber of the eye. Thus, this study has identified TCF8 as the gene responsible for approximately half of the cases of PPCD, has implicated TCF8 mutations in developmental abnormalities outside the eye, and has presented the TCF8 regulatory target, COL4A3, as a key, shared molecular component of two different diseases, PPCD and Alport syndrome.

Autoantigens↗
PubMed2005

Stargardt-like macular dystrophy protein ELOVL4 exerts a dominant negative effect by recruiting wild-type protein into aggresomes.

PURPOSE: Mutations in the gene Elongation of very long-chain fatty acids-4 (ELOVL4) have been shown to be associated with autosomal dominant Stargardt-like macular dystrophy (STGD3). ELOVL4 is expressed in photoreceptors and encodes a putative transmembrane protein of 314 amino acids with an endoplasmic reticulum (ER) retention signal. A 5 bp deletion in exon 6 of ELOVL4 observed in some STGD3 patients results in the truncation of the protein and loss of the ER retention signal. To understand the disease mechanism underlying STGD3 we studied the intracellular trafficking of the wild-type and a 5 bp deletion mutant of ELOVL4. METHODS: Wild-type and mutant ELOVL4 proteins with the N-terminal GFP/V5 tags were expressed in COS-7 cells. Expression and the intracellular localization of the wild-type and mutant proteins were characterized by immunocytochemistry and western blot analysis using tag- and organelle-specific antibodies. Interaction between the wild-type and mutant proteins was studied by two-dimensional gel electrophoresis and fluorescence resonance energy transfer (FRET) analysis. RESULTS: The mutant ELOVL4 protein exerted a dominant negative effect when the wild-type and 5 bp deletion mutant ELOVL4 proteins were co-expressed in COS-7 cells. Immunocytochemical analysis, two-dimensional gel electrophoresis and FRET revealed that the mutant ELOVL4 interacts with the wild-type protein, forming higher molecular mass complexes that accumulate in aggresomes. CONCLUSIONS: In the presence of mutant ELOVL4 protein, the wild-type protein was recruited into perinuclear cytoplasmic inclusions that resemble aggresomes. The interaction between the wild-type and mutant forms of ELOVL4 and the resultant alteration in the trafficking of the wild-type ELOVL4 protein suggest a mechanism for the pathogenicity observed in patients with autosomal dominant STGD3.

Animals↗
PubMed2005

Early-onset macular degeneration with drusen in a cynomolgus monkey (Macaca fascicularis) pedigree: exclusion of 13 candidate genes and loci.

PURPOSE: To describe hereditary macular degeneration observed in the cynomolgus monkey (Macaca fascicularis), which shares phenotypic features with age-related macular degeneration in humans, and to test the involvement of candidate gene loci by mutation screening and linkage analysis. METHODS: Ophthalmic examinations with fundus photography, fluorescein angiography (FA), indocyanine green angiography (IA), electroretinography (ERG), and histologic studies were performed on both affected and unaffected monkeys in the pedigree. The monkey orthologues of the human ABCA4, VMD2, EFEMP1, TIMP3, and ELOVL4 genes were cloned and screened for mutations by single-strand conformation polymorphism (SSCP) analysis or denaturing high-performance liquid chromatography (DHPLC) and direct sequencing in six affected and five unaffected monkeys from the pedigree and in six unrelated, unaffected monkeys. Subsequently, 13 human macular degeneration loci including these five genes were analyzed to test for linkage with the disease. Nineteen affected and seven unaffected monkeys in the pedigree were analyzed by using human microsatellite markers linked to the 13 loci. RESULTS: Yellowish white spots were observed in the macula and fovea centralis, and in some cases the spots scattered to the peripheral retina along the blood vessels. FA showed hyperfluorescence corresponding to the dots except in the foveola. No anomalies were found by IA and ERG. Histologic studies demonstrated that the spots were drusen. Mutation analysis of the ABCA4, VMD2, EFEMP1, TIMP3, and ELOVL4 genes identified a few sequence variants, but none of them segregated with the disease. Linkage analysis with markers linked to these five genes and an additional eight human macular degeneration loci failed to establish linkage. Haplotype analysis excluded the involvement of the 13 candidate loci for harboring the gene associated with macular degeneration in the monkeys. CONCLUSIONS: Significant homology was identified between monkey and human orthologues of the five macular degeneration genes. Thirteen loci associated with macular degeneration in humans or harboring macular degeneration genes were excluded as causal of early-onset macular degeneration in the monkeys. It is likely that none of these loci, but rather a novel gene, is involved in causing the observed phenotype in this monkey pedigree.

ATP-Binding Cassette Transporters↗
PubMed2005

Sequencing arrays for screening multiple genes associated with early-onset human retinal degenerations on a high-throughput platform.

PURPOSE: To develop and apply microarray-based resequencing technology to detect sequence alterations in multiple autosomal recessive retinal disease genes on a single high-throughput platform. METHODS: Oligonucleotides corresponding to both strands of the target exons and the flanking intron sequences of 29,214 bp from 11 genes associated with autosomal recessive retinitis pigmentosa (arRP) were tiled on 20 x 25-microm microarrays (arRP-I arrays). A total of 155 exons were amplified from 35 arRP patient DNA samples, with each sample being sequenced on an arRP-I chip by hybridization. RESULTS: With the arRP-I arrays, 97.6% of the tiled sequence were determined with more than 99% accuracy and reproducibility. Of the 2.4% unread sequence, 89.5% involved stretches of G or C. In analyzing the 903,140-bp sequence from the 35 patient samples, 506 sequence changes have been detected in which 386 are previously reported alterations, and 120 are novel. In addition to four known causative mutations, six novel sequence changes that are potentially pathogenic were observed. Additional analysis is needed to determine whether these changes are responsible for arRP in these patients. CONCLUSIONS: The use of microarray for sequencing is a novel approach, and the arRP-I chip is the first successful application of this technology for determining sequence alteration in multiple disease-related genes. These arrays can be used for high-throughput genotyping of patients with relevant retinal conditions. In addition, these arrays offer a unique opportunity to interrogate complex patterns of inheritance due to the involvement of more than one gene by screening multiple genes on a single platform.

Base Sequence↗
PubMed2005

Late-onset macular degeneration and long anterior lens zonules result from a CTRP5 gene mutation.

PURPOSE: To identify the gene responsible for a complex ocular phenotype of late-onset macular degeneration, long anterior zonules (LAZ), and elevated intraocular pressure (IOP) and to study its expression. METHODS: Ocular examination, visual field, fluorescein angiography, and electrophysiology testing were performed. One affected individual was treated with vitamin A. DNA from 55 family members (UM:H389) was used for linkage, mapping, and mutation analysis. Linkage analysis of macular degeneration and LAZ phenotypes was performed independently. Mutations in candidate genes were screened by sequencing. mRNA expression of CTRP5 and MFRP, which are bicistronic genes, was studied by semiquantitative RT-PCR (qRT-PCR) in various human tissues. CTRP5 expression was also evaluated by in situ hybridization. RESULTS: Affected members had LAZ detectable by the third decade and/or macular degeneration by the fourth to fifth decade. A six-month treatment with vitamin A shortened dark adaptation considerably in one affected member. Both conditions mapped independently with zero recombination to 11q23, with maximum lod scores of 3.31 for macular degeneration and 5.41 for LAZ. The same CTRP5 missense mutation was identified in all affected individuals. Retinal pigment epithelium (RPE) and ciliary epithelium (CE) showed highest CTRP5 transcript expression, which was also true for MFRP. CTRP5 tissue expression was confirmed by in situ hybridization. CONCLUSIONS: A single locus at 11q23 is implicated in a complex ocular phenotype involving RPE and CE, tissues of neuroectodermal origin. All individuals with either LAZ and/or macular degeneration carry the same CTRP5 S163R mutation, which is transmitted in autosomal dominant manner.

Adult↗
PubMed2004

Characterization of mouse orthologue of ELOVL4: genomic organization and spatial and temporal expression.

Mutations in ELOVL4 are associated with dominant macular degeneration (adMD/STGD3). This gene is highly expressed in the retina and is conserved through evolution. Here we report the genomic organization of the mouse orthologue of ELOVL4 and its temporal and spatial expression. A significant amount of ELOVL4 mRNA expression is detected in the adult retina, brain, skin, testis, and lens. During development, expression is first noted at embryonic day 7 (E7). A significant level of the mRNA is observed both in brain and in eyes at postnatal day 1 (P1), after which levels decrease in the brain and increase in the retina until they stabilize at P30. ELOVL4 protein is evident in the ocular tissues by E10.5 and becomes restricted predominantly to the photoreceptor layer in the mature retina. These observations suggest that ELOVL4 may play an important role in embryonic development and in maintaining normal physiology of retina and brain at later stages of development.

Animals↗
PubMed2004

Atrophic macular degeneration mutations in ELOVL4 result in the intracellular misrouting of the protein.

Elongation of very long chain fatty acids 4 (ELOVL4) is a novel member of the ELO family of genes that are involved in fatty acid metabolism. ELOVL4 encodes a putative transmembrane protein of 314 amino acids that carries a possible endoplasmic reticulum (ER) retention/retrieval signal (KXKXX) at the C-terminus. Two distinct mutations, a 5-bp deletion and a complex mutation from the same region in exon 6 of this gene, have been reported so far and are associated with autosomal dominant atrophic macular degeneration (adMD/STGD3). Both of these deletions could result in C-terminal truncation and loss of the ER retention signal in the mutant protein. We expressed the wild-type and mutant proteins in COS-7 and CHO cells to study the intracellular distribution of ELOVL4 and to identify possible implications of the above mutations in its localization. Immunofluorescence analysis of these proteins along with organelle marker antibodies revealed predominant ER localization for wild-type ELOVL4. Targeted deletion of the dilysine motif at the C-terminus of the protein resulted in the loss of ER localization. Immunoelectron microscopy and immunofluorescence analysis revealed a similar ER localization pattern for the protein in human photoreceptors. These data indicate that ELOVL4 is an ER-resident protein, which supports its suggested function in fatty acid elongation. We also demonstrate that the localization of both mutant proteins was dramatically changed from an ER to a Golgi distribution. Our observations suggest that the consequences of defective protein trafficking could underlie the molecular mechanism associated with degeneration of the macula in the patients with adMD/STGD3.

Amino Acid Motifs↗
PubMed2003

Evaluation of the ELOVL4 gene in patients with autosomal recessive retinitis pigmentosa and Leber congenital amaurosis.

PURPOSE: To determine whether pathogenic mutations exist in the ELOVL4 gene in patients with inherited retinal degenerations other than Stargardt-like macular dystrophy or other hereditary macular degenerations. METHODS: All six exons comprising the open reading frame of the ELOVL4 gene were evaluated by single-strand conformation analysis, direct nucleotide sequencing, or both methods. RESULTS: No pathogenic mutations were found among 84 patients with autosomal recessive retinitis pigmentosa or among 51 patients with Leber congenital amaurosis (congenital retinal blindness). CONCLUSIONS: These data support the conclusion that recessive retinitis pigmentosa and Leber congenital amaurosis are rarely if ever associated with changes in the ELOVL4 gene.

Blindness↗
PubMed2003

Evolutionarily conserved ELOVL4 gene expression in the vertebrate retina.

PURPOSE: The gene elongation of very long chain fatty acids-4 (ELOVL4) has been shown to underlie phenotypically heterogeneous forms of autosomal dominant macular degeneration. In this study, the extent of evolutionary conservation and the existence and localization of retinal expression of this gene was investigated across a wide variety of species. METHODS: Southern blot analysis of genomic DNA and bioinformatic analysis using the human ELOVL4 cDNA and protein sequences, respectively, were performed to identify species in which ELOVL4 orthologues and/or homologues are present. Retinal RNA and protein extracts derived from different species were assessed by Northern hybridization and immunoblot techniques to assess evolutionary conservation of gene expression. Immunohistochemical analysis of tissue sections prepared from various mammalian retinas was performed to determine the distribution of ELOVL4 and homologous proteins within specific retinal cell layers. RESULTS: The existence of ELOVL4 sequence orthologues and homologues was confirmed by both Southern blot analysis and in silico searches of protein sequence databases. Phylogenetic analysis places ELOVL4 among a large family of known and putative fatty acid elongase proteins. Northern blot analysis revealed the presence of multiple transcripts corresponding to ELOVL4 homologues expressed in the retina of several different mammalian species. Conserved proteins were also detected among retinal extracts of different mammals and were found to localize predominantly to the photoreceptor cell layer within retinal tissue preparations. CONCLUSIONS: The ELOVL4 gene is highly conserved throughout evolution and is expressed in the photoreceptor cells of the retina in a variety of different species, which suggests that it plays a critical role in retinal cell biology.

Amino Acid Sequence↗