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520 High resolution transcriptome profiling identifies gene expression signatures unique to normal human keratinocytes, dermal fibroblasts, and endothelial cells
Genetic Disease, Gene Regulation and Gene Therapy | ABSTRACTS 516
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Functional annotation of genes underlying hair disorders R Severin and L Petukhova Columbia University, NY, NY In an age of precision medicine and personalized diagnoses, as we are faced with interpreting the genome sequences of patients, it becomes critical to understand both the spectrum of genes that could be contributing to a particular clinical presentation, and the pathways mediating genetic effects. Gene mapping in humans and animal models has identified hundreds of genes that underlie hair disorders, affecting the hair cycle, hair follicle density, and hair fiber length, texture or pigmentation, among other characteristics. Here, we compiled a list of 489 hair disorder genes reported in the literature and/or public databases and performed functional annotations. Gene ontology enrichment identified 545 pathways significantly enriched by 479 of these genes. Surprisingly, 128 of these genes are annotated to influence development of a tissue or organ other than skin, including brain, heart, lung, skeletal and reproductive organs, among others; 27 genes are annotated to play a role in drug response; and 26 genes are involved in various cellular metabolic processes. Pathway analysis identified 85 functional pathways significantly enriched by 184 of the 489 genes. Of interest, 87 of these genes fall within one or more cancer pathways, including not only melanoma and basal cell carcinoma, but also glioma and prostate, pancreatic, thyroid, lung, endometrial, and colorectal cancers, among others; 57 genes enrich at least one of 12 pathogen response pathways; 18 genes are active in signaling pathways regulating stem cell pluripotency. A total of 26 significantly enriched pathways involve cellular signaling, including PI3K-Akt, MAPK, Ras, Rap1, adipocytokine, thyroid hormone, NF-kappaB, ErbB, FoxO, Hippo, sphingolipid, Wnt, Hedgehog, EGF, and neurotrophin among others. Importantly, disease genes that share GO annotations or fall within the same pathway have more similar phenotypic consequences than genes that do not. Our work in functionally annotating genes underlying hair disorders provides a valuable resource for both the research and clinical communities embarking on precision medicine initiatives for skin and hair disorders.
Disseminated disease despite low mutant allele fractions: The variable phenotype of mosaic tuberous sclerosis complex N Nathan1, L Hamieh2, M Tyburczy2, J Wang1, O Oyerinde3, J Moss3, D Kwiatkowski2 and T Darling1 1 Uniformed Services University, Bethesda, MD, 2 Brigham and Women’s Hospital, Boston, MA and 3 Cardiovascular and Pulmonary Branch, National Heart, Lung, and Blood Institute, NIH, Bethesda, MD Mosaicism has been suggested to explain tuberous sclerosis complex (TSC) manifesting as unilateral angiofibromas or as mild disease and no mutation identified using standard genetic testing. To identify mosaicism and its phenotypic spectrum in TSC, we performed next generation sequencing (NGS) on DNA isolated from TSC skin tumors, including angiofibromas, ungual fibromas, shagreen patch, oral fibroma, and fibrous cephalic plaque. Mosaicism was identified in 17/30 patients, first by identification of mutations in TSC2 in DNA from 28 skin tumors from the 17 patients, of which 16 had two mutations consistent with Knudson’s twohit hypothesis. The mutant allele fractions in whole tumors or cultured tumor cells ranged from 1 to 54%. A shared mutation in TSC2 was identified in every case where more than one tumor was studied from a single patient. The median mutant allele fraction was 5% in blood samples (range 0-19, n¼11) and 1.4% in other control tissues (range 0-13, n¼13), well below the 50% allelic fraction expected for germline mutations. Examination of these mosaic adult women with TSC revealed that 4 had unilateral or asymmetric angiofibromas, 3 had fewer than 20 angiofibromas, and 10 had numerous bilateral facial angiofibromas. Overall these results show that: 1) analysis of DNA from whole skin tumors or cultured tumor cells enables identification of low-level mosaicism using NGS, and 2) the phenotype of mosaic TSC patients varies from those with unilateral angiofibromas and mild disease to those with a disseminated phenotype that may be indistinguishable from those with germline mutations.
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ATAC-seq analysis of chromatin accessibility in skin-homing T cells Z Zhang1, A Tsoi1, J Kitzman2, RP Nair3, P Stuart4 and J Elder1 1 Dept. of Dermatology, U.of Michigan, Ann Arbor, MI, 2 Dept. of Human Genetics, U. of Michigan, Ann Arbor, MI, 3 University of Michigan, Ann Arbor, MI and 4 Dept. of Dermatology, Univ. of Michigan, Ann Arbor, MI Genome-wide association studies (GWAS) of psoriasis have identified 84 psoriasis susceptibility loci. Most of the genetic signals do not alter protein structure, but instead are regulatory in nature. Functional annotation of these GWAS hits demonstrated that psoriasis genetic signals are enriched in regulatory elements from different T cells (CD8+ and CD4+ T-cells including Th0, Th1, and Th17). Based on these findings, we developed a protocol for isolation of skin-homing T-cells from PBMC, based on the presence of cutaneous lymphocyte-associated antigen (CLA). In order to understand the regulatory significance of psoriasis genetic signals, we performed genomewide analysis of open chromatin regions (OCR) using Assay for Transposase-Accessible Chromatin and sequencing (ATAC-seq) (Nat Methods 10:1213). OCR sequence reads, which suggest the location of regulatory elements, were processed and mapped using UCSC genome tracks. Meanwhile, both non-skin-homing and skin-homing T cells were activated by anti-CD3/CD28 to model the immune response. Indicative of cell type specificity, the CD4 and CD8 gene loci were selectively accessible in CD4 and CD8 T-cells, respectively, with the OCRs closely matching patterns present in UCSC ENCODE DNaseeseq tracks. Compared with unstimulated skin-homing T cells, 24-hour stimulated skin-homing T cells exhibited increased chromatin accessibility across the activation marker gene CD69 as well as the FUT7 gene, which encodes the fucosyltransferase 7 that is specific for skin homing T-cells. By expanding our sample to w150 individuals (normal and psoriatic), and by determining the genome-wide overlay of GWAS, ATAC-seq, and global transcriptome data, we will elucidate how the regulomes of psoriasis-relevant immunocytes are perturbed by psoriasis-associated genetic variation.
Phase I/IIa clinical trial for recessive dystrophic epidermolysis bullosa using genetically corrected autologous keratinocytes Z Siprashvili1, N Nguyen2, E Gorell2, K Loutit2, Y Dutt-Singkh3, J Nazaroff3, P Khuu1, L Furukawa2, H Lorenz2, T Leung4, D Keene5, K Rieger2, PA Khavari6, A Lane2, JY Tang3 and M Marinkovich1 1 Stanford University School of Medicine, Stanford, CA, 2 Stanford U, Stanford, CA, 3 Stanford University, Stanford, CA, 4 UPEN, Philadelphia, PA, 5 Shriners Hospital for Children, Portland, OR and 6 Stanford University School of Medicine; VA Palo Alto, Stanford, CA Recessive Dystrophic Epidermolysis Bullosa (RDEB) is an inherited genetic skin disorder caused by mutations in the COL7A1 gene encoding type VII collagen (C7). We report the results of the ongoing Phase I/IIa clinical trial of ex vivo gene therapy for the treatment of severe RDEB. 6 adult subjects (mean age 26) enrolled in this trial carried various heterozygous COL7A1 mutations resulting in expression of only truncated C7 protein and displayed absent, or sparse rudimentary anchoring fibrils (AF) by EM. Autologous RDEB keratinocytes isolated from skin biopsies were transduced with GMP grade retrovirus carrying full-length COL7A1. 6 w35cm2 autologous epidermal sheets were grafted onto chronic wounds that were unhealed for a mean of 8.5 years. The primary endpoint is to evaluate wound healing compared to untreated wound. Secondary endpoints included expression of C7 and restoration of AF at 3 and 6 months. No serious adverse events were reported, and no replication competent virus detected for up to 3 years. At 3 months, 94% (27/36 grafts), at 6 months, 67% (16/24 grafts) and at 12 months 50% (12/24 grafts) showed significant wound healing defined as > 75% healing compared with baseline. C7 expression and morphologically normal NC2 reactive AF were demonstrated at the BMZ of graft biopsies for up to 2 years however expression gradually diminished over time. These data demonstrate that COL7A1 ex-vivo gene transfer has a favorable safety profile and wound healing efficacy thus highlighting the potential of cell based therapy in RDEB patients.
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High resolution transcriptome profiling identifies gene expression signatures unique to normal human keratinocytes, dermal fibroblasts, and endothelial cells MA Beamer1, WR Swindell2, L Tsoi1, P Tsou1, Y Li3, MK Sarkar1, X Xing1, Y Liang1, GJ Fisher4 and JE Gudjonsson1 1 University of Michigan, Ann Arbor, MI, 2 Ohio University, Athens, OH, 3 Department of Dermatology, University of Michigan, Ann arbor, MI and 4 Department of Dermatology, University of Michigan, Ann Arbor, MI The majority of skin is composed of three major cell types: keratinocytes (KC), fibroblasts (FB) and endothelial cells (EC). These account for the majority of RNA from healthy human skin, but no study has used RNA-seq to evaluate the gene expression signature unique to each cell type. To address this, we grew out these three major cell constituents from human skin (KC, FB, EC, n¼3-4 each) and performed high-resolution RNA-seq profiling. Using a threshold of 2-fold change and FDR of < 0.1, 1892 genes were increased and 1673 were decreased in KC vs FB+EC. Increased genes in KCs included SERPINB3 and -B13 (26377- and 25906-fold, p¼1.8E-80 and p¼1.6E-73 respectively). Enriched gene-ontology (GO) categories included epidermis development (p¼6.1E30), peptide cross-linking (p¼2E-21), and retinol metabolism (p¼0.001). In contrast FB had 1376 increased and 1017 decreased genes compared to KC+EC. Increased genes included the collagen genes COL8A2 and COL10A1 (69- and 73-fold, p¼1.5E-19 and p¼2.9E-14 respectively). GO categories enriched and unique to FBs included collagen fibril organization (p¼1.8E-11), appendage development (p¼1.7E-08), and cell-matrix adhesion (5.3E-6). Finally, ECs had 1468 increased and 1439 decreased genes compared to KC+FB. Increased genes included ANGPT2 (1760-fold, p¼6.6E-42). GO categories enriched in ECs included intracellular signaling cascade (p-1.1R-9), regulation of angiogenesis (p¼1.4E-6), and protein kinase cascade p¼1.9E-04). 10038 genes were expressed by all three cell types (KC, FB and EC). GO categories enriched included cellular housekeeping functions such as translation (p¼5.4E-75) and generation of precursor metabolites (p¼4.9E-30). Our data show that cells extracted and grown from skin maintain tissuespecific transcriptomic features. These data can guide functional studies and deconvolute expression patterns of tissues into cell type-specific components.
Genome-wide single nucleotide polymorphism-based autozygosity mapping facilitates identification of mutations in consanguineous families with epidermolysis bullosa M Zahabiyon1, H Vahidnezhad2, L Youssefian1, A Saeidian1, S Zeinali3, S Sotoudeh4, N Mozafari4, J Bradfield5, C Kim5, H Hakonarson5 and J Uitto1 1 TJU, Philadelphia, PA, 2 TJU, Pasteur Institute, Philadelphia, PA, 3 Pasteur Institute, Tehran, Iran, 4 TUMS, Tehran, Iran and 5 CHOP, Philadelphia, PA Epidermolysis bullosa (EB), is phenotypically heterogeneous and known to be caused by mutations in as many as 18 genes with autosomal dominant or recessive inheritance. Identification of specific genes is critical for molecular confirmation of the clinical diagnosis and allows precise subclassificationwith prognostic implications. In this study, we have ascertained an Iranian cohort of 46 consanguineous EB families of unknown subtype. To find the appropriate candidate genes for sequencing by the next generation sequencing panel or Sanger sequencing, we applied autozygosity mapping with genome-wide single nucleotide polymorphism (SNP) array consisting of 550,000 markers and by locus specific short tandem repeat (STR) markers of nine most common EB related genes in Iranian population. The families affected by an unknown subtype of EB were subjected to autozygosity mapping which suggested candidate genes in 43 probands. Among the 46 families, mutations were disclosed in 40 of them, 39 being homozygous. Among the 35 distinct mutations identified in 8 different genes, 19 were previously unreported. Inability to find candidate genes by homozygosity mapping in 3 families was due to the presence of compound heterozygous mutations or due to filtering out the homozygosity blocks at 2 Mb. Collectively, genome-wide SNP-based autozygosity mapping facilitates identification of candidate genes in EB families. The specific mutation information forms the platform for prenatal testing and preimplantation genetic diagnosis, as well as for development of allele-specific therapies in the realm of precision medicine for this group of currently intractable disorders.
www.jidonline.org S89
517
Functional annotation of genes underlying hair disorders R Severin and L Petukhova Columbia University, NY, NY In an age of precision medicine and personalized diagnoses, as we are faced with interpreting the genome sequences of patients, it becomes critical to understand both the spectrum of genes that could be contributing to a particular clinical presentation, and the pathways mediating genetic effects. Gene mapping in humans and animal models has identified hundreds of genes that underlie hair disorders, affecting the hair cycle, hair follicle density, and hair fiber length, texture or pigmentation, among other characteristics. Here, we compiled a list of 489 hair disorder genes reported in the literature and/or public databases and performed functional annotations. Gene ontology enrichment identified 545 pathways significantly enriched by 479 of these genes. Surprisingly, 128 of these genes are annotated to influence development of a tissue or organ other than skin, including brain, heart, lung, skeletal and reproductive organs, among others; 27 genes are annotated to play a role in drug response; and 26 genes are involved in various cellular metabolic processes. Pathway analysis identified 85 functional pathways significantly enriched by 184 of the 489 genes. Of interest, 87 of these genes fall within one or more cancer pathways, including not only melanoma and basal cell carcinoma, but also glioma and prostate, pancreatic, thyroid, lung, endometrial, and colorectal cancers, among others; 57 genes enrich at least one of 12 pathogen response pathways; 18 genes are active in signaling pathways regulating stem cell pluripotency. A total of 26 significantly enriched pathways involve cellular signaling, including PI3K-Akt, MAPK, Ras, Rap1, adipocytokine, thyroid hormone, NF-kappaB, ErbB, FoxO, Hippo, sphingolipid, Wnt, Hedgehog, EGF, and neurotrophin among others. Importantly, disease genes that share GO annotations or fall within the same pathway have more similar phenotypic consequences than genes that do not. Our work in functionally annotating genes underlying hair disorders provides a valuable resource for both the research and clinical communities embarking on precision medicine initiatives for skin and hair disorders.
Disseminated disease despite low mutant allele fractions: The variable phenotype of mosaic tuberous sclerosis complex N Nathan1, L Hamieh2, M Tyburczy2, J Wang1, O Oyerinde3, J Moss3, D Kwiatkowski2 and T Darling1 1 Uniformed Services University, Bethesda, MD, 2 Brigham and Women’s Hospital, Boston, MA and 3 Cardiovascular and Pulmonary Branch, National Heart, Lung, and Blood Institute, NIH, Bethesda, MD Mosaicism has been suggested to explain tuberous sclerosis complex (TSC) manifesting as unilateral angiofibromas or as mild disease and no mutation identified using standard genetic testing. To identify mosaicism and its phenotypic spectrum in TSC, we performed next generation sequencing (NGS) on DNA isolated from TSC skin tumors, including angiofibromas, ungual fibromas, shagreen patch, oral fibroma, and fibrous cephalic plaque. Mosaicism was identified in 17/30 patients, first by identification of mutations in TSC2 in DNA from 28 skin tumors from the 17 patients, of which 16 had two mutations consistent with Knudson’s twohit hypothesis. The mutant allele fractions in whole tumors or cultured tumor cells ranged from 1 to 54%. A shared mutation in TSC2 was identified in every case where more than one tumor was studied from a single patient. The median mutant allele fraction was 5% in blood samples (range 0-19, n¼11) and 1.4% in other control tissues (range 0-13, n¼13), well below the 50% allelic fraction expected for germline mutations. Examination of these mosaic adult women with TSC revealed that 4 had unilateral or asymmetric angiofibromas, 3 had fewer than 20 angiofibromas, and 10 had numerous bilateral facial angiofibromas. Overall these results show that: 1) analysis of DNA from whole skin tumors or cultured tumor cells enables identification of low-level mosaicism using NGS, and 2) the phenotype of mosaic TSC patients varies from those with unilateral angiofibromas and mild disease to those with a disseminated phenotype that may be indistinguishable from those with germline mutations.
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ATAC-seq analysis of chromatin accessibility in skin-homing T cells Z Zhang1, A Tsoi1, J Kitzman2, RP Nair3, P Stuart4 and J Elder1 1 Dept. of Dermatology, U.of Michigan, Ann Arbor, MI, 2 Dept. of Human Genetics, U. of Michigan, Ann Arbor, MI, 3 University of Michigan, Ann Arbor, MI and 4 Dept. of Dermatology, Univ. of Michigan, Ann Arbor, MI Genome-wide association studies (GWAS) of psoriasis have identified 84 psoriasis susceptibility loci. Most of the genetic signals do not alter protein structure, but instead are regulatory in nature. Functional annotation of these GWAS hits demonstrated that psoriasis genetic signals are enriched in regulatory elements from different T cells (CD8+ and CD4+ T-cells including Th0, Th1, and Th17). Based on these findings, we developed a protocol for isolation of skin-homing T-cells from PBMC, based on the presence of cutaneous lymphocyte-associated antigen (CLA). In order to understand the regulatory significance of psoriasis genetic signals, we performed genomewide analysis of open chromatin regions (OCR) using Assay for Transposase-Accessible Chromatin and sequencing (ATAC-seq) (Nat Methods 10:1213). OCR sequence reads, which suggest the location of regulatory elements, were processed and mapped using UCSC genome tracks. Meanwhile, both non-skin-homing and skin-homing T cells were activated by anti-CD3/CD28 to model the immune response. Indicative of cell type specificity, the CD4 and CD8 gene loci were selectively accessible in CD4 and CD8 T-cells, respectively, with the OCRs closely matching patterns present in UCSC ENCODE DNaseeseq tracks. Compared with unstimulated skin-homing T cells, 24-hour stimulated skin-homing T cells exhibited increased chromatin accessibility across the activation marker gene CD69 as well as the FUT7 gene, which encodes the fucosyltransferase 7 that is specific for skin homing T-cells. By expanding our sample to w150 individuals (normal and psoriatic), and by determining the genome-wide overlay of GWAS, ATAC-seq, and global transcriptome data, we will elucidate how the regulomes of psoriasis-relevant immunocytes are perturbed by psoriasis-associated genetic variation.
Phase I/IIa clinical trial for recessive dystrophic epidermolysis bullosa using genetically corrected autologous keratinocytes Z Siprashvili1, N Nguyen2, E Gorell2, K Loutit2, Y Dutt-Singkh3, J Nazaroff3, P Khuu1, L Furukawa2, H Lorenz2, T Leung4, D Keene5, K Rieger2, PA Khavari6, A Lane2, JY Tang3 and M Marinkovich1 1 Stanford University School of Medicine, Stanford, CA, 2 Stanford U, Stanford, CA, 3 Stanford University, Stanford, CA, 4 UPEN, Philadelphia, PA, 5 Shriners Hospital for Children, Portland, OR and 6 Stanford University School of Medicine; VA Palo Alto, Stanford, CA Recessive Dystrophic Epidermolysis Bullosa (RDEB) is an inherited genetic skin disorder caused by mutations in the COL7A1 gene encoding type VII collagen (C7). We report the results of the ongoing Phase I/IIa clinical trial of ex vivo gene therapy for the treatment of severe RDEB. 6 adult subjects (mean age 26) enrolled in this trial carried various heterozygous COL7A1 mutations resulting in expression of only truncated C7 protein and displayed absent, or sparse rudimentary anchoring fibrils (AF) by EM. Autologous RDEB keratinocytes isolated from skin biopsies were transduced with GMP grade retrovirus carrying full-length COL7A1. 6 w35cm2 autologous epidermal sheets were grafted onto chronic wounds that were unhealed for a mean of 8.5 years. The primary endpoint is to evaluate wound healing compared to untreated wound. Secondary endpoints included expression of C7 and restoration of AF at 3 and 6 months. No serious adverse events were reported, and no replication competent virus detected for up to 3 years. At 3 months, 94% (27/36 grafts), at 6 months, 67% (16/24 grafts) and at 12 months 50% (12/24 grafts) showed significant wound healing defined as > 75% healing compared with baseline. C7 expression and morphologically normal NC2 reactive AF were demonstrated at the BMZ of graft biopsies for up to 2 years however expression gradually diminished over time. These data demonstrate that COL7A1 ex-vivo gene transfer has a favorable safety profile and wound healing efficacy thus highlighting the potential of cell based therapy in RDEB patients.
520
521
High resolution transcriptome profiling identifies gene expression signatures unique to normal human keratinocytes, dermal fibroblasts, and endothelial cells MA Beamer1, WR Swindell2, L Tsoi1, P Tsou1, Y Li3, MK Sarkar1, X Xing1, Y Liang1, GJ Fisher4 and JE Gudjonsson1 1 University of Michigan, Ann Arbor, MI, 2 Ohio University, Athens, OH, 3 Department of Dermatology, University of Michigan, Ann arbor, MI and 4 Department of Dermatology, University of Michigan, Ann Arbor, MI The majority of skin is composed of three major cell types: keratinocytes (KC), fibroblasts (FB) and endothelial cells (EC). These account for the majority of RNA from healthy human skin, but no study has used RNA-seq to evaluate the gene expression signature unique to each cell type. To address this, we grew out these three major cell constituents from human skin (KC, FB, EC, n¼3-4 each) and performed high-resolution RNA-seq profiling. Using a threshold of 2-fold change and FDR of < 0.1, 1892 genes were increased and 1673 were decreased in KC vs FB+EC. Increased genes in KCs included SERPINB3 and -B13 (26377- and 25906-fold, p¼1.8E-80 and p¼1.6E-73 respectively). Enriched gene-ontology (GO) categories included epidermis development (p¼6.1E30), peptide cross-linking (p¼2E-21), and retinol metabolism (p¼0.001). In contrast FB had 1376 increased and 1017 decreased genes compared to KC+EC. Increased genes included the collagen genes COL8A2 and COL10A1 (69- and 73-fold, p¼1.5E-19 and p¼2.9E-14 respectively). GO categories enriched and unique to FBs included collagen fibril organization (p¼1.8E-11), appendage development (p¼1.7E-08), and cell-matrix adhesion (5.3E-6). Finally, ECs had 1468 increased and 1439 decreased genes compared to KC+FB. Increased genes included ANGPT2 (1760-fold, p¼6.6E-42). GO categories enriched in ECs included intracellular signaling cascade (p-1.1R-9), regulation of angiogenesis (p¼1.4E-6), and protein kinase cascade p¼1.9E-04). 10038 genes were expressed by all three cell types (KC, FB and EC). GO categories enriched included cellular housekeeping functions such as translation (p¼5.4E-75) and generation of precursor metabolites (p¼4.9E-30). Our data show that cells extracted and grown from skin maintain tissuespecific transcriptomic features. These data can guide functional studies and deconvolute expression patterns of tissues into cell type-specific components.
Genome-wide single nucleotide polymorphism-based autozygosity mapping facilitates identification of mutations in consanguineous families with epidermolysis bullosa M Zahabiyon1, H Vahidnezhad2, L Youssefian1, A Saeidian1, S Zeinali3, S Sotoudeh4, N Mozafari4, J Bradfield5, C Kim5, H Hakonarson5 and J Uitto1 1 TJU, Philadelphia, PA, 2 TJU, Pasteur Institute, Philadelphia, PA, 3 Pasteur Institute, Tehran, Iran, 4 TUMS, Tehran, Iran and 5 CHOP, Philadelphia, PA Epidermolysis bullosa (EB), is phenotypically heterogeneous and known to be caused by mutations in as many as 18 genes with autosomal dominant or recessive inheritance. Identification of specific genes is critical for molecular confirmation of the clinical diagnosis and allows precise subclassificationwith prognostic implications. In this study, we have ascertained an Iranian cohort of 46 consanguineous EB families of unknown subtype. To find the appropriate candidate genes for sequencing by the next generation sequencing panel or Sanger sequencing, we applied autozygosity mapping with genome-wide single nucleotide polymorphism (SNP) array consisting of 550,000 markers and by locus specific short tandem repeat (STR) markers of nine most common EB related genes in Iranian population. The families affected by an unknown subtype of EB were subjected to autozygosity mapping which suggested candidate genes in 43 probands. Among the 46 families, mutations were disclosed in 40 of them, 39 being homozygous. Among the 35 distinct mutations identified in 8 different genes, 19 were previously unreported. Inability to find candidate genes by homozygosity mapping in 3 families was due to the presence of compound heterozygous mutations or due to filtering out the homozygosity blocks at 2 Mb. Collectively, genome-wide SNP-based autozygosity mapping facilitates identification of candidate genes in EB families. The specific mutation information forms the platform for prenatal testing and preimplantation genetic diagnosis, as well as for development of allele-specific therapies in the realm of precision medicine for this group of currently intractable disorders.
www.jidonline.org S89