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Yang Y, Wang C, Liu Y, Li G, Wang X, Wang H, He D. Comparative transcriptomic analyses reveal key genes underlying melanin distribution during embryonic development in geese ( Anser anser). Br Poult Sci 2024; 65:387-393. [PMID: 38748993 DOI: 10.1080/00071668.2024.2335943] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2023] [Accepted: 03/08/2024] [Indexed: 07/27/2024]
Abstract
1. Melanin distribution typically exhibits a gradient dilution along the dorsal-ventral axis of the body, including in domestic geese. However, the specific genes and molecular mechanisms responsible for this melanin distribution pattern remain incompletely understood.2. The transcriptomic comparisons were conducted at three embryonic stages, specifically on embryonic d 15 (E15), 22 (E22), and 29 (E29), between the pigmented dorsal skin and the depigmented distal foot.3. Differentially expressed genes (DEGs) associated with melanin synthesis were identified, particularly TYR, TYRP1, and EDNRB2, which exhibited significantly higher expression levels in the dorsal skin at E15 and E22. However, expression levels significantly decreased in later stages (E29).4. The ASIP gene showed remarkably high-expression levels in the distal feet compared to the dorsal skin post-E22 stage (log2FC: 5.31/6.88 at E22/E29). Gene Ontology (GO) enrichment analysis detected eight terms associated with melanin synthesis and melanosome formation (p < 0.05), including melanosome membrane (GO: 0033162) and melanin biosynthetic process (GO: 0042438). Additionally, KEGG pathway analysis showed significant enrichment of the melanogenesis pathway (hsa004916) at d 22 (E22).
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Affiliation(s)
- Y Yang
- Institute of Animal Husbandry and Veterinary Science, Shanghai Academy of Agricultural Science, Shanghai, China
| | - C Wang
- Institute of Animal Husbandry and Veterinary Science, Shanghai Academy of Agricultural Science, Shanghai, China
| | - Y Liu
- Institute of Animal Husbandry and Veterinary Science, Shanghai Academy of Agricultural Science, Shanghai, China
| | - G Li
- Institute of Animal Husbandry and Veterinary Science, Shanghai Academy of Agricultural Science, Shanghai, China
| | - X Wang
- Institute of Animal Husbandry and Veterinary Science, Shanghai Academy of Agricultural Science, Shanghai, China
| | - H Wang
- Institute of Animal Husbandry and Veterinary Science, Shanghai Academy of Agricultural Science, Shanghai, China
| | - D He
- Institute of Animal Husbandry and Veterinary Science, Shanghai Academy of Agricultural Science, Shanghai, China
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2
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Elkin J, Martin A, Courtier-Orgogozo V, Santos ME. Analysis of the genetic loci of pigment pattern evolution in vertebrates. Biol Rev Camb Philos Soc 2023; 98:1250-1277. [PMID: 37017088 DOI: 10.1111/brv.12952] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Revised: 03/08/2023] [Accepted: 03/14/2023] [Indexed: 04/06/2023]
Abstract
Vertebrate pigmentation patterns are amongst the best characterised model systems for studying the genetic basis of adaptive evolution. The wealth of available data on the genetic basis for pigmentation evolution allows for analysis of trends and quantitative testing of evolutionary hypotheses. We employed Gephebase, a database of genetic variants associated with natural and domesticated trait variation, to examine trends in how cis-regulatory and coding mutations contribute to vertebrate pigmentation phenotypes, as well as factors that favour one mutation type over the other. We found that studies with lower ascertainment bias identified higher proportions of cis-regulatory mutations, and that cis-regulatory mutations were more common amongst animals harbouring a higher number of pigment cell classes. We classified pigmentation traits firstly according to their physiological basis and secondly according to whether they affect colour or pattern, and identified that carotenoid-based pigmentation and variation in pattern boundaries are preferentially associated with cis-regulatory change. We also classified genes according to their developmental, cellular, and molecular functions. We found a greater proportion of cis-regulatory mutations in genes implicated in upstream developmental processes compared to those involved in downstream cellular functions, and that ligands were associated with a higher proportion of cis-regulatory mutations than their respective receptors. Based on these trends, we discuss future directions for research in vertebrate pigmentation evolution.
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Affiliation(s)
- Joel Elkin
- Department of Zoology, University of Cambridge, Downing Street, Cambridge, CB2 3EJ, UK
| | - Arnaud Martin
- Department of Biological Sciences, The George Washington University, 800 22nd St. NW, Suite 6000, Washington, DC, 20052, USA
| | | | - M Emília Santos
- Department of Zoology, University of Cambridge, Downing Street, Cambridge, CB2 3EJ, UK
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Brown AR, Comai K, Mannino D, McCullough H, Donekal Y, Meyers HC, Graves CW, Seidel HS. A community-science approach identifies genetic variants associated with three color morphs in ball pythons (Python regius). PLoS One 2022; 17:e0276376. [PMID: 36260636 PMCID: PMC9581371 DOI: 10.1371/journal.pone.0276376] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Accepted: 10/05/2022] [Indexed: 11/13/2022] Open
Abstract
Color morphs in ball pythons (Python regius) provide a unique and largely untapped resource for understanding the genetics of coloration in reptiles. Here we use a community-science approach to investigate the genetics of three color morphs affecting production of the pigment melanin. These morphs-Albino, Lavender Albino, and Ultramel-show a loss of melanin in the skin and eyes, ranging from severe (Albino) to moderate (Lavender Albino) to mild (Ultramel). To identify genetic variants causing each morph, we recruited shed skins of pet ball pythons via social media, extracted DNA from the skins, and searched for putative loss-of-function variants in homologs of genes controlling melanin production in other vertebrates. We report that the Albino morph is associated with missense and non-coding variants in the gene TYR. The Lavender Albino morph is associated with a deletion in the gene OCA2. The Ultramel morph is associated with a missense variant and a putative deletion in the gene TYRP1. Our study is one of the first to identify genetic variants associated with color morphs in ball pythons and shows that pet samples recruited from the community can provide a resource for genetic studies in this species.
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Affiliation(s)
- Autumn R. Brown
- Department of Biology, Eastern Michigan University, Ypsilanti, MI, United States of America
| | - Kaylee Comai
- Department of Biology, Eastern Michigan University, Ypsilanti, MI, United States of America
| | - Dominic Mannino
- Department of Biology, Eastern Michigan University, Ypsilanti, MI, United States of America
| | - Haily McCullough
- Department of Biology, Eastern Michigan University, Ypsilanti, MI, United States of America
| | - Yamini Donekal
- Department of Biology, Eastern Michigan University, Ypsilanti, MI, United States of America
| | - Hunter C. Meyers
- Department of Biology, Eastern Michigan University, Ypsilanti, MI, United States of America
| | - Chiron W. Graves
- Department of Biology, Eastern Michigan University, Ypsilanti, MI, United States of America
- * E-mail: (CWG); (HSS)
| | - Hannah S. Seidel
- Department of Biology, Eastern Michigan University, Ypsilanti, MI, United States of America
- * E-mail: (CWG); (HSS)
| | - The BIO306W Consortium
- Department of Biology, Eastern Michigan University, Ypsilanti, MI, United States of America
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Kalds P, Zhou S, Gao Y, Cai B, Huang S, Chen Y, Wang X. Genetics of the phenotypic evolution in sheep: a molecular look at diversity-driving genes. Genet Sel Evol 2022; 54:61. [PMID: 36085023 PMCID: PMC9463822 DOI: 10.1186/s12711-022-00753-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2022] [Accepted: 08/29/2022] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND After domestication, the evolution of phenotypically-varied sheep breeds has generated rich biodiversity. This wide phenotypic variation arises as a result of hidden genomic changes that range from a single nucleotide to several thousands of nucleotides. Thus, it is of interest and significance to reveal and understand the genomic changes underlying the phenotypic variation of sheep breeds in order to drive selection towards economically important traits. REVIEW Various traits contribute to the emergence of variation in sheep phenotypic characteristics, including coat color, horns, tail, wool, ears, udder, vertebrae, among others. The genes that determine most of these phenotypic traits have been investigated, which has generated knowledge regarding the genetic determinism of several agriculturally-relevant traits in sheep. In this review, we discuss the genomic knowledge that has emerged in the past few decades regarding the phenotypic traits in sheep, and our ultimate aim is to encourage its practical application in sheep breeding. In addition, in order to expand the current understanding of the sheep genome, we shed light on research gaps that require further investigation. CONCLUSIONS Although significant research efforts have been conducted in the past few decades, several aspects of the sheep genome remain unexplored. For the full utilization of the current knowledge of the sheep genome, a wide practical application is still required in order to boost sheep productive performance and contribute to the generation of improved sheep breeds. The accumulated knowledge on the sheep genome will help advance and strengthen sheep breeding programs to face future challenges in the sector, such as climate change, global human population growth, and the increasing demand for products of animal origin.
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Affiliation(s)
- Peter Kalds
- Key Laboratory of Animal Genetics, Breeding and Reproduction of Shaanxi Province, College of Animal Science and Technology, Northwest A&F University, Yangling, 712100 China
- Department of Animal and Poultry Production, Faculty of Environmental Agricultural Sciences, Arish University, El-Arish, 45511 Egypt
| | - Shiwei Zhou
- Key Laboratory of Animal Genetics, Breeding and Reproduction of Shaanxi Province, College of Animal Science and Technology, Northwest A&F University, Yangling, 712100 China
- College of Veterinary Medicine, Northwest A&F University, Yangling, 712100 China
| | - Yawei Gao
- Key Laboratory of Animal Genetics, Breeding and Reproduction of Shaanxi Province, College of Animal Science and Technology, Northwest A&F University, Yangling, 712100 China
| | - Bei Cai
- Key Laboratory of Animal Genetics, Breeding and Reproduction of Shaanxi Province, College of Animal Science and Technology, Northwest A&F University, Yangling, 712100 China
| | - Shuhong Huang
- Key Laboratory of Animal Genetics, Breeding and Reproduction of Shaanxi Province, College of Animal Science and Technology, Northwest A&F University, Yangling, 712100 China
| | - Yulin Chen
- Key Laboratory of Animal Genetics, Breeding and Reproduction of Shaanxi Province, College of Animal Science and Technology, Northwest A&F University, Yangling, 712100 China
- International Joint Agriculture Research Center for Animal Bio-Breeding, Ministry of Agriculture and Rural Affairs, Yangling, 712100 China
| | - Xiaolong Wang
- Key Laboratory of Animal Genetics, Breeding and Reproduction of Shaanxi Province, College of Animal Science and Technology, Northwest A&F University, Yangling, 712100 China
- International Joint Agriculture Research Center for Animal Bio-Breeding, Ministry of Agriculture and Rural Affairs, Yangling, 712100 China
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Pazzola M, Vacca GM, Paschino P, Bittante G, Dettori ML. Novel Genes Associated with Dairy Traits in Sarda Sheep. Animals (Basel) 2021; 11:ani11082207. [PMID: 34438665 PMCID: PMC8388407 DOI: 10.3390/ani11082207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Revised: 07/09/2021] [Accepted: 07/23/2021] [Indexed: 11/16/2022] Open
Abstract
The aim of the present research was to analyze the variability of 45 SNPs from different genes involved in metabolism and innate immunity to perform an association analysis with the milk yield, composition and milk coagulation traits. A population of 1112 Sarda breed sheep was sampled. Genotyping was generated by a TaqMan Open ArrayTM. Thirty out of the 45 SNPs were polymorphic, and 12 displayed a minor allele frequency higher than 0.05. An association analysis showed that the variability at genes PRKAG3 and CD14 was significantly associated with the daily milk yield. The variability at PRKAG3 was also associated with the protein and casein content, somatic cell score and bacterial score. The variation at the PRKAA2 gene was associated with the milk lactose concentration. The SNPs at CD14 were also associated with the traditional milk coagulation properties, while the SNPs at GHR and GHRHR were associated with kSR, a derived coagulation parameter related to the rate of syneresis. The information provided here is new and increases our knowledge of genotype-phenotype interactions in sheep. Our findings might be useful in appropriate breeding schemes to be set up for the Sarda sheep breed, but these should be confirmed by further studies, possibly performed on independent populations.
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Affiliation(s)
- Michele Pazzola
- Department of Veterinary Medicine, University of Sassari, Via Vienna 2, 07100 Sassari, SS, Italy; (M.P.); (P.P.); (M.L.D.)
| | - Giuseppe Massimo Vacca
- Department of Veterinary Medicine, University of Sassari, Via Vienna 2, 07100 Sassari, SS, Italy; (M.P.); (P.P.); (M.L.D.)
- Correspondence: ; Tel.: +39-079229442
| | - Pietro Paschino
- Department of Veterinary Medicine, University of Sassari, Via Vienna 2, 07100 Sassari, SS, Italy; (M.P.); (P.P.); (M.L.D.)
| | - Giovanni Bittante
- Department of Agronomy, Food, Natural Resources, Animals and Environment (DAFNAE), University of Padova, Viale dell’Università 16, 35020 Legnaro, PD, Italy;
| | - Maria Luisa Dettori
- Department of Veterinary Medicine, University of Sassari, Via Vienna 2, 07100 Sassari, SS, Italy; (M.P.); (P.P.); (M.L.D.)
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Analysis of MC1R, MITF, TYR, TYRP1, and MLPH Genes Polymorphism in Four Rabbit Breeds with Different Coat Colors. Animals (Basel) 2021; 11:ani11010081. [PMID: 33466315 PMCID: PMC7824738 DOI: 10.3390/ani11010081] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2020] [Revised: 12/31/2020] [Accepted: 12/31/2020] [Indexed: 12/28/2022] Open
Abstract
Simple Summary Coat color is an important breed characteristic and economic trait for rabbits, and it is regulated by a few genes. In this study, the gene frequencies of some pigmentation genes were investigated in four Chinese native rabbit breeds with different coat colors. A total of 14 genetic variants were detected in the gene fragments of MC1R, MITF, TYR, TYRP1, and MLPH genes, and there was low-to-moderate polymorphism in the populations. The gene frequency showed significant differences among the four rabbit populations. The above results suggest that these genetic variations play an important role in regulating the coat color of rabbits. This study will provide potential molecular markers for the breeding of coat color traits in rabbits. Abstract Pigmentation genes such as MC1R, MITF, TYR, TYRP1, and MLPH play a major role in rabbit coat color. To understand the genotypic profile underlying coat color in indigenous Chinese rabbit breeds, portions of the above-mentioned genes were amplified and variations in them were analyzed by DNA sequencing. Based on the analysis of 24 Tianfu black rabbits, 24 Sichuan white rabbits, 24 Sichuan gray rabbits, and 24 Fujian yellow rabbits, two indels in MC1R, three SNPs in MITF, five SNPs (single nucleotide polymorphisms) in TYR, one SNP in TYRP1, and three SNPs in MLPH were discovered. These variations have low-to-moderate polymorphism, and there are significant differences in their distribution among the different breeds (p < 0.05). These results provide more information regarding the genetic background of these native rabbit breeds and reveal their high-quality genetic resources.
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Compound heterozygous PLA2G6 loss-of-function variants in Swaledale sheep with neuroaxonal dystrophy. Mol Genet Genomics 2020; 296:235-242. [PMID: 33159255 PMCID: PMC7840627 DOI: 10.1007/s00438-020-01742-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Accepted: 10/23/2020] [Indexed: 10/28/2022]
Abstract
Sporadic occurrences of neurodegenerative disorders including neuroaxonal dystrophy (NAD) have been previously reported in sheep. However, so far no causative genetic variant has been found for ovine NAD. The aim of this study was to characterize the phenotype and the genetic aetiology of an early-onset neurodegenerative disorder observed in several lambs of purebred Swaledale sheep, a native English breed. Affected lambs showed progressive ataxia and stiff gait and subsequent histopathological analysis revealed the widespread presence of axonal spheroid indicating neuronal degeneration. Thus, the observed clinical phenotype could be explained by a novel form of NAD. After SNP genotyping and subsequent linkage mapping within a paternal half-sib pedigree with a total of five NAD-affected lambs, we identified two loss-of-function variants by whole-genome sequencing in the ovine PLA2G6 gene situated in a NAD-linked genome region on chromosome 3. All cases were carriers of a compound heterozygous splice site variant in intron 2 and a nonsense variant in exon 8. Herein we present evidence for the occurrence of a familial novel form of recessively inherited NAD in sheep due to allelic heterogeneity at PLA2G6. This study reports two pathogenic variants in PLA2G6 causing a novel form of NAD in Swaledale sheep which enables selection against this fatal disorder.
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Letko A, Dijkman R, Strugnell B, Häfliger IM, Paris JM, Henderson K, Geraghty T, Orr H, Scholes S, Drögemüller C. Deleterious AGXT Missense Variant Associated with Type 1 Primary Hyperoxaluria (PH1) in Zwartbles Sheep. Genes (Basel) 2020; 11:E1147. [PMID: 33003365 PMCID: PMC7600965 DOI: 10.3390/genes11101147] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2020] [Revised: 09/15/2020] [Accepted: 09/26/2020] [Indexed: 11/23/2022] Open
Abstract
Severe oxalate nephropathy has been previously reported in sheep and is mostly associated with excessive oxalate in the diet. However, a rare native Dutch breed (Zwartbles) seems to be predisposed to an inherited juvenile form of primary hyperoxaluria and no causative genetic variant has been described so far. This study aims to characterize the phenotype and genetic etiology of the inherited metabolic disease observed in several purebred Zwartbles sheep. Affected animals present with a wide range of clinical signs including condition loss, inappetence, malaise, and, occasionally, respiratory signs, as well as an apparent sudden unexpected death. Histopathology revealed widespread oxalate crystal deposition in kidneys of the cases. Whole-genome sequencing of two affected sheep identified a missense variant in the ovine AGXT gene (c.584G>A; p.Cys195Tyr). Variants in AGXT are known to cause type I primary hyperoxaluria in dogs and humans. Herein, we present evidence that the observed clinicopathological phenotype can be described as a form of ovine type I primary hyperoxaluria. This disorder is explained by a breed-specific recessively inherited pathogenic AGXT variant. Genetic testing enables selection against this fatal disorder in Zwartbles sheep as well as more precise diagnosis in animals with similar clinical phenotype. Our results have been incorporated in the Online Mendelian Inheritance in Animals (OMIA) database (OMIA 001672-9940).
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Affiliation(s)
- Anna Letko
- Institute of Genetics, Vetsuisse Faculty, University of Bern, 3012 Bern, Switzerland; (A.L.); (I.M.H.); (J.M.P.)
| | | | - Ben Strugnell
- Farm Post Mortems Ltd., Hamsterley, Bishop Auckland, County Durham DL13 3QF, UK;
| | - Irene M. Häfliger
- Institute of Genetics, Vetsuisse Faculty, University of Bern, 3012 Bern, Switzerland; (A.L.); (I.M.H.); (J.M.P.)
| | - Julia M. Paris
- Institute of Genetics, Vetsuisse Faculty, University of Bern, 3012 Bern, Switzerland; (A.L.); (I.M.H.); (J.M.P.)
| | - Katrina Henderson
- SRUC Consulting Veterinary Services, Pentlands Science Park, Bush Estate Loan, Penicuik, Midlothian EH26 0PZ, UK; (K.H.); (T.G.); (H.O.); (S.S.)
| | - Tim Geraghty
- SRUC Consulting Veterinary Services, Pentlands Science Park, Bush Estate Loan, Penicuik, Midlothian EH26 0PZ, UK; (K.H.); (T.G.); (H.O.); (S.S.)
| | - Hannah Orr
- SRUC Consulting Veterinary Services, Pentlands Science Park, Bush Estate Loan, Penicuik, Midlothian EH26 0PZ, UK; (K.H.); (T.G.); (H.O.); (S.S.)
| | - Sandra Scholes
- SRUC Consulting Veterinary Services, Pentlands Science Park, Bush Estate Loan, Penicuik, Midlothian EH26 0PZ, UK; (K.H.); (T.G.); (H.O.); (S.S.)
| | - Cord Drögemüller
- Institute of Genetics, Vetsuisse Faculty, University of Bern, 3012 Bern, Switzerland; (A.L.); (I.M.H.); (J.M.P.)
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Paris JM, Letko A, Häfliger IM, Ammann P, Drögemüller C. Ear type in sheep is associated with the MSRB3 locus. Anim Genet 2020; 51:968-972. [PMID: 32805068 DOI: 10.1111/age.12994] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/27/2020] [Indexed: 12/01/2022]
Abstract
Ear morphology is an important determinant of sheep breeds. It includes different variable traits such as ear size and erectness, suggesting a polygenic architecture. Here, we performed a comprehensive genome-wide analysis to identify regions under selection for ear morphology in 515 sheep from 17 breeds fixed for diverse ear phenotypes using 34k SNP genotyping data. GWASs for two ear type traits, size and erectness, revealed a single genome-wide significant association on ovine chromosome 3. The derived marker alleles were enriched in sheep with large and/or floppy ears. The GWAS signal harboured the MSRB3 gene encoding methionine sulphoxide reductase B3, which has already been found to be associated with different ear types in other species. We attempted whole-genome resequencing to identify causal variant(s) within a 1 Mb interval around MSRB3. This experiment excluded major copy number variants in the interval, but failed to identify a compelling candidate causal variant. Fine-mapping suggested that the causal variant for large floppy ears most likely resides in a 175 kb interval downstream of the MSRB3 coding region.
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Affiliation(s)
- J M Paris
- Vetsuisse Faculty, Institute of Genetics, University of Bern, Bern, 3001, Switzerland
| | - A Letko
- Vetsuisse Faculty, Institute of Genetics, University of Bern, Bern, 3001, Switzerland
| | - I M Häfliger
- Vetsuisse Faculty, Institute of Genetics, University of Bern, Bern, 3001, Switzerland
| | - P Ammann
- ProSpecieRara, Basel, 4052, Switzerland
| | - C Drögemüller
- Vetsuisse Faculty, Institute of Genetics, University of Bern, Bern, 3001, Switzerland
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Paris JM, Letko A, Häfliger IM, Švara T, Gombač M, Klinc P, Škibin A, Pogorevc E, Drögemüller C. A de novo variant in OTX2 in a lamb with otocephaly. Acta Vet Scand 2020; 62:5. [PMID: 31969185 PMCID: PMC6977343 DOI: 10.1186/s13028-020-0503-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Accepted: 01/13/2020] [Indexed: 12/03/2022] Open
Abstract
Background Otocephaly is a rare lethal malformation of the first branchial arch. While the knowledge on the causes of otocephaly in animals is limited, different syndromic forms in man are associated with variants of the PRRX1 and OTX2 genes. Case presentation A stillborn male lamb of the Istrian Pramenka sheep breed showed several congenital craniofacial anomalies including microstomia, agnathia, aglossia, and synotia. In addition, the lamb had a cleft palate, a small opening in the ventral neck region, a cystic oesophagus and two hepatic cysts. The brain was normally developed despite the deformed shape of the head. Taken together the findings led to a diagnosis of otocephaly. Whole-genome sequencing was performed from DNA of the affected lamb and both parents revealing a heterozygous single nucleotide variant in the OTX2 gene (Chr7: 71478714G > A). The variant was absent in both parents and therefore due to a de novo mutation event. It was a nonsense variant, XM_015097088.2:c.265C > T; which leads to an early premature stop codon and is predicted to truncate more than 70% of the OTX2 open reading frame (p.Arg89*). Conclusions The genetic findings were consistent with the diagnosis of the otocephaly and provide strong evidence that the identified loss-of-function variant is pathogenic due to OTX2 haploinsufficiency. The benefits of trio-based whole-genome sequencing as an emerging tool in veterinary pathology to confirm diagnosis are highlighted.
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