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Polydactyly was recorded before 100 BCE and attracted widespread interest because of its relationship to limb health and ancestral traits in horses. However, the underlying reasons for the development of polydactyly remain unclear. To search for polydactyly-related genes, we utilize a paternal half-sib family and screen for variants that match the mode of inheritance. Through this screening process, 77 variants in 65 genes are filtered. A missense variant (EqCab3.0 chr4: <107353368> A > G) (rs1138485164) in the 3rd exon of LMBR1 is identified as a source of amino acid sequence variation. Gene editing confirms that the variant down-regulates LMBR1expression, increases the proliferative viability of mutant cells, and inhibits apoptosis. This study suggests that LMBR1 might play a role in the development of polydactyly and that the variant detected in this study is related to polydactyly in horses. However, further research is needed to determine whether a direct relationship exists., (© 2024. The Author(s).)

Polydactyly is a genetic abnormality that affects both pig welfare and industry profits. Despite efforts to explore the genetic basis of pig polydactyly, progress remains limited. In this study, we analyzed a group of Large White pigs with postaxial polydactyly, including 29 cases and 79 controls from 24 families. High-depth sequencing was performed on 20 pigs, while low-depth sequencing was improved through imputation for the remaining pigs. A genome-wide association study (GWAS) and genetic differentiation were conducted using the resequencing dataset, resulting in the identification of 48 significantly associated SNPs and 27 candidate regions. The genetic differentiation regions on chromosomes 5 and 18, which harbored GWAS-identified SNPs, were delineated as confidence regions. The confidence region at Chr18: 1.850-1.925 Mb covers the fifth intron of LMBR1, a gene that contains an important regulatory element for SHH, known as ZRS. Mutations in this ZRS have been found to cause polydactyly in animals and humans. Therefore, we propose LMBR1 as a prospective candidate gene for postaxial polydactyly. These findings emphasize the importance of exploring the role of ZRS within LMBR1 in the pathogenesis of polydactyly in pigs., (© 2024 Stichting International Foundation for Animal Genetics.)

Mutations in serologically defined colon cancer autoantigen protein 8 ( SDCCAG8 ) were first identified in retinal ciliopathy families a decade ago with unknown function. To investigate the pathogenesis of SDCCAG8-associated retinal ciliopathies in vivo , we employed CRISPR/Cas9-mediated homology-directed recombination (HDR) to generate two knock-in mouse models, Sdccag8 Y236X/Y236X and Sdccag8 E451GfsX467/E451GfsX467 , which carry truncating mutations of the mouse Sdccag8 , corresponding to mutations that cause Bardet-Biedl syndrome (BBS) and Senior-Løken syndrome (SLS) (c.696T>G p.Y232X and c.1339-1340insG p.E447GfsX463) in humans, respectively. The two mutant Sdccag8 knock-in mice faithfully recapitulated human SDCCAG8-associated BBS phenotypes such as rod-cone dystrophy, cystic renal disorder, polydactyly, infertility, and growth retardation, with varied age of onset and severity depending on the hypomorphic strength of the Sdccag8 mutations. To the best of our knowledge, these knock-in mouse lines are the first BBS mouse models to present with the polydactyly phenotype. Major phototransduction protein mislocalization was also observed outside the outer segment after initiation of photoreceptor degeneration. Impaired cilia were observed in the mutant photoreceptors, renal epithelial cells, and mouse embryonic fibroblasts derived from the knock-in mouse embryos, suggesting that SDCCAG8 plays an essential role in ciliogenesis, and cilium defects are a primary driving force of SDCCAG8-associated retinal ciliopathies.

Polydactyly is a congenital malformation resulting from an autosomal dominant mutation manifesting as supernumerary digits of the hands or feet. It is most commonly reported in humans and domestic mammals, though there have also been isolated examples across a range of wild vertebrate species. Here we report a case of extremely unusual bilateral preaxial polydactyly on the pectoral limbs of a male western grey kangaroo (Macropus fuliginosus) from the South West region of Western Australia, in which two supernumerary digits were present on each manus. A supernumerary digit I on each manus was rudimentary in morphology without extrinsic muscular connections. However, supernumerary digit II present on each manus had fully developed extrinsic and intrinsic muscular connections, suggesting that these digits possessed normal function in flexion and extension. An alternative hypothesis is that the two supernumerary digits are both representatives of the most radial digit I, though this would then require the true digit I to have taken on the appearance of digit II by acquiring an additional phalanx and modified muscular attachments. The carpal bones exhibited a number of subtle differences in morphology when compared to normal pentadactyl individuals. The presence of a distal, rather than proximal, epiphysis on the first metacarpal was unexpected but further investigation suggested that this characteristic is perhaps more variable (in this species at least) than has been previously recognized. This case provides an unusual example to be considered within the broader context of limb development., (© 2020 American Association for Anatomy.)

Objectives: Polydactyly has been described in two breeds of domestic cats (Maine Coon and Pixie Bob) and in some outbred domestic cats (eg, Hemingway cats). In most cases, feline polydactyly is a non-syndromic preaxial polydactyly. Three variants located in a regulatory sequence involved in limb development, named ZRS (zone of polarising activity regulatory sequence), have been identified to be responsible for feline polydactyly. These variants have been found in outbred domestic cats in the UK ( UK1 and UK2 variants) and in Hemingway cats in the USA ( Hw variant). The aim of this study was to characterise the genetic features of polydactyly in Maine Coon cats., Methods: Genotyping assay was used to identify the variant(s) segregating in a cohort of 75 polydactyl and non-polydactyl Maine Coon cats from different breeding lines from Europe, Canada and the USA. The authors performed a segregation analysis to identify the inheritance pattern of polydactyly in this cohort and analysed the population structure., Results: The Hw allele was identified in a subset of polydactyl cats. Sequencing of two regulatory sequences involved in limb development did not reveal any other variant in polydactyl cats lacking the Hw allele. Additionally, genotype-phenotype and segregation analyses revealed the peculiar inheritance pattern of polydactyly in Maine Coon cats. The population structure analysis demonstrated a genetic distinction between Hw and Hw -free polydactyl cats., Conclusions and Relevance: Polydactyly in Maine Coon cats is inherited as an autosomal dominant trait with incomplete penetrance and variable expressivity, and this trait is characterised by genetic heterogeneity in the Maine Coon breed. Maine Coon breeders should be aware of this situation and adapt their breeding practices accordingly.

An immature Alpine swift ( Tachymarptis melba ) that presented to a wildlife rehabilitation center was observed to have bilateral pentadactyly on examination. The supernumerary digits did not appear to cause discomfort for the bird, and no motor deficits were apparent. The skin and nails of the digits appeared normal. Radiographically, the extra digits appeared to be composed of two phalanges. The male swift was housed and fed an insectivore diet until it was fully fledged and demonstrated good flying ability. After 16 days of hospitalization, hand-feeding, and flight training, the bird was released to the wild. To our knowledge, this is the first case described of bilateral pentadactyly in an Alpine swift., (© 2018 by the Association of Avian Veterinarians.)

The Beijing You chicken is a Chinese native breed with superior meat quality and a unique appearance. The G/T mutation of SNP rs80659072 in the Shh long-range regulator of GGA2 is highly associated with the polydactyly phenotype in some chicken breeds. In the present study, this SNP was genotyped using the TaqMan detection method, and its association with the number of toes was analyzed in a flock of 158 birds of the Beijing You population maintained at the Beijing Academy of Agriculture and Forestry Sciences. Furthermore, the skeletal structure of the digits was dissected and assembled in 113 birds. The findings revealed that the toes of Beijing You chickens were rich and more complex than expected. The plausible mutation rs80659072 in the zone of polarizing activity regulatory sequence (ZRS) in chickens was an essential but not sufficient condition for polydactyly and polyphalangy in Beijing You chickens. Several individuals shared the T allele but showed normal four-digit conformations. However, breeding trials demonstrated that the T allele could serve as a strong genetic marker for five-toe selection in Beijing You chickens.

Objectives Polydactyly has been reported in a number of vertebrate species, including the domestic cat. It is a common characteristic in some breeding lines of the Maine Coon. The aim of this study was to assess the limb phenotype of polydactyl cats using physical and radiographic examinations. Methods We used physical examination and radiography to characterise the polydactyly phenotype in a cohort of 70 Maine Coon cats, including 48 polydactyl cats from four different breeding lines from Europe, Canada and the USA. Results The phenotypic expression of polydactyly showed great variability, not only in digit number and conformation, but also in the structure of the carpus and tarsus. Comparison of the size of the radius in polydactyl and non-polydactyl 3-month-old kittens and adult females did not reveal any difference between polydactyl and non-polydactyl cats. Conclusions and relevance We conclude that polydactyly in Maine Coon cats is characterised by broad phenotypic diversity. Polydactyly not only affects digit number and conformation, but also carpus and tarsus conformation, with no apparent deleterious consequence on feline welfare.

Recently, it has been found that spontaneous mutation Lx (polydactyly-luxate syndrome) in the rat is determined by deletion of a conserved intronic sequence of the Plzf (Promyelocytic leukemia zinc finger protein) gene. In addition, Plzf is a prominent candidate gene for quantitative trait loci (QTLs) associated with cardiac hypertrophy and fibrosis in the spontaneously hypertensive rat (SHR). In the current study, we tested the effects of Plzf gene targeting in the SHR using TALENs (transcription activator-like effector nucleases). SHR ova were microinjected with constructs pTAL438/439 coding for a sequence-specific endonuclease that binds to target sequence in the first coding exon of the Plzf gene. Out of 43 animals born after microinjection, we detected a single male founder. Sequence analysis revealed a deletion of G that resulted in frame shift mutation starting in codon 31 and causing a premature stop codon at position of amino acid 58. The Plzftm1Ipcv allele is semi-lethal since approximately 95% of newborn homozygous animals died perinatally. All homozygous animals exhibited manifestations of a caudal regression syndrome including tail anomalies and serious size reduction and deformities of long bones, and oligo- or polydactyly on the hindlimbs. The heterozygous animals only exhibited the tail anomalies. Impaired development of the urinary tract was also revealed: one homozygous and one heterozygous rat exhibited a vesico-ureteric reflux with enormous dilatation of ureters and renal pelvis. In the homozygote, this was combined with a hypoplastic kidney. These results provide evidence for the important role of Plzf gene during development of the caudal part of a body-column vertebrae, hindlimbs and urinary system in the rat., Competing Interests: The authors have declared that no competing interests exist.

The chicken has been a particularly useful model for the study of craniofacial development and disease for over a century due to their relatively large size, accessibility, and amenability for classical bead implantation and transplant experiments. Several naturally occurring mutant lines with craniofacial anomalies also exist and have been heavily utilized by developmental biologist for several decades. Two of the most well known lines, talpid(2) (ta(2)) and talpid(3) (ta(3)), represent the first spontaneous mutants to have the causative genes identified. Despite having distinct genetic causes, both mutants have recently been identified as ciliopathic. Excitingly, both of these mutants have been classified as models for human craniofacial ciliopathies: Oral-facial-digital syndrome (ta(2)) and Joubert syndrome (ta(3)). Herein, we review and compare these two models of craniofacial disease and highlight what they have revealed about the molecular and cellular etiology of ciliopathies. Furthermore, we outline how applying classical avian experiments and new technological advances (transgenics and genome editing) with naturally occurring avian mutants can add a tremendous amount to what we currently know about craniofacial ciliopathies., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Polydactyly is one of the most common hereditary congenital limb malformations in chickens and other vertebrates. The zone of polarizing activity regulatory sequence (ZRS) is critical for the development of polydactyly. The causative mutation of polydactyly in the Silkie chicken has been mapped to the ZRS; however, the causative mutations of other chicken breeds are yet to be established. To understand whether the same mutation decides the polydactyly phenotype in other chicken breeds, we detected the single-nucleotide polymorphism in 26 different chicken breeds, specifically, 24 Chinese indigenous breeds and 2 European breeds. The mutation was found to have fully penetrated chickens with polydactyly in China, indicating that it is causative for polydactyly in Chinese indigenous chickens. In comparison, the mutation showed no association with polydactyly in Houdan chickens, which originate from France, Europe. Based on the different morphology of polydactyly in Chinese and European breeds, we assumed that the trait might be attributable to different genetic foundations. Therefore, we subsequently performed genome-wide association analysis (GWAS) to locate the region associated with polydactyly. As a result, a ~0.39 Mb genomic region on GGA2p was identified. The region contains six candidate genes, with the causative mutation found in Chinese indigenous breeds also being located in this region. Our results demonstrate that polydactyly in chickens from China and Europe is caused by two independent mutation events that are closely located in the chicken genome.

We report the first two cases of polydactyly in an atelid species: (i) a wild ca. 16-week-old infant female presenting seven digits in both feet and other bone malformations and (ii) a wild newborn male presenting six digits in both feet with the extra digit fused to the hallux., (© 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

This report describes a case of polydactyly in the hind-limb of a West African Dwarf goat kid in South West Africa. Physical examination revealed the presence of four digits in each of the hind limbs. Radiological examination and macerated bones of the animal showed a bifid shape of each metatarsal that was more prominent from the distal half of the diaphysis. This resulted in the presence of four articulating surfaces per limb at the distal extremity. Though this condition is rare in goats, we advise that continuous reporting by researchers can give a better prevalence statistics of these occurrences.

Two pigs were identified having "extra feet" (preaxial polydactyly) within a purebred population of Yorkshire pigs. Polydactyly is an inherited disorder in many species that may be controlled by either recessive or dominant genes. Experimental matings were conducted using pigs that had produced affected offspring with the result of 12 polydactyl offspring out of 95 piglets. One polydactyl-producing boar was also mated to 4 Duroc sows and 8 distantly related Yorkshire sows to produce 129 unaffected offspring. Together, these results suggest a recessive mode of inheritance, possibly with incomplete penetrance. Candidate genes, LMBR1, EN2, HOXA10-13, GLI3, WNT2, WNT16, and SHH, were identified based on association with similar phenotypes in other species. Homologues for these genes are all found on SSC18. Sequencing and linkage studies showed no evidence for association with HOXA10-13, WNT2, and WNT16. Results for the regions including GLI3, LMBR1, and SHH, however, were inconclusive. A whole genome scan was conducted on DNA samples from 10 affected pigs and 12 close relatives using the Illumina PorcineSNP60 BeadChip and compared with 69 more distantly related animals in the same population. No evidence was found for a major gene causing polydactyly. However, a 25-Mb stretch of homozygosity on SSC8 was identified as fairly unique to the family segregating for this trait. Therefore, this chromosome segment may play a role in development of polydactyly in concert with other genes.

Case Description: Two feline littermates were presented to the Auburn University Small Animal Clinic at the age of approximately 10 weeks. Both cats had varus thoracic limb deformities bilaterally and pelvic limb polydactyly., Clinical Findings: Radiographs revealed bilateral radial hypoplasia (hemimelia), generalised cardiomegaly, and pelvic limb polydactyly., Treatment and Outcome: No treatment was instituted. Cardiopulmonary changes will be monitored periodically., Clinical Relevance: The heritability of radial hemimelia has been suggested, but has yet to be proven. In utero environmental causes (teratogens) are another possible cause of congenital radial hemimelia. The presence of bilateral pelvic limb polydactyly, bilateral radial hemimelia, and generalised cardiomegaly in feline littermates may offer more information on the origins of this orthopaedic disorder and the potential undesirable results that can occur when breeding polydactyl cats or cats affected by radial hemimelia.

Canine preaxial polydactyly (PPD) in the hind limb is a developmental trait that restores the first digit lost during canine evolution. Using a linkage analysis, we previously demonstrated that the affected gene in a Korean breed is located on canine chromosome 16. The candidate locus was further limited to a linkage disequilibrium (LD) block of <213 kb composing the single gene, LMBR1, by LD mapping with single nucleotide polymorphisms (SNPs) for affected individuals from both Korean and Western breeds. The ZPA regulatory sequence (ZRS) in intron 5 of LMBR1 was implicated in mammalian polydactyly. An analysis of the LD haplotypes around the ZRS for various dog breeds revealed that only a subset is assigned to Western breeds. Furthermore, two distinct affected haplotypes for Asian and Western breeds were found, each containing different single-base changes in the upstream sequence (pZRS) of the ZRS. Unlike the previously characterized cases of PPD identified in the mouse and human ZRS regions, the canine mutations in pZRS lacked the ectopic expression of sonic hedgehog in the anterior limb bud, distinguishing its role in limb development from that of the ZRS.

A male, 10 month old llama with malformation of both front limbs was presented. Both front limbs had one more digit located medially. The distal phalanx of this additional digit at the left front limb reached the ground by the tip of the keratinzed pad and the toenail. The accessory digit at the right front limb was bent in a 90 degree angle caudolateraly. Beside the digital bones of the accessory digits the second metacarpal bone and the first carpal bone could be detected in both front limbs by radiological examination. Secondary a bilateral slight carpal valgus deformity could be seen.

The following case report describes the diagnosis and surgery of bilateral polydactyly of unknown origin in a colt. A 7-month-old Berber colt was referred for cosmetic and curative excision of supernumerary digits. Radiographic examination revealed bilateral polydactyly and welldeveloped first carpal bones. Surgery consisted of an osteotomy of both second metacarpal bones combined with an amputation of the supernumerary digits. The follow-up at 18 months after surgery revealed a sound horse with an excellent cosmetic outcome.

A case of monomelic forelimb ectrodactyly (lobster-claw deformity) in a West Highland white terrier is reported. Clinical and radiographic findings are described. The dog was treated with a soft tissue reconstruction of the cleft. It later developed a slight varus-type deformity at the carpus but remained sound with occasional bouts of mild lameness following vigorous exercise. To the author's knowledge, this is the first reported case of canine ectrodactyly treated by simple cleft reconstruction, and only the second report of ectrodactyly in this breed.

A female German Holstein twin calf showed polydactyly in both front limbs and in one of the hind limbs. In three limbs an additional medial toe was seen. No malformations of the limbs were present in the male twin partner and four maternal half sibs. The analysis of the pedigree revealed that the affected calf had common ancestors. The coefficient of inbreeding of the affected calf was 1.312%. As a monogenic or digenic inheritance was suspected in similar cases, it may be probable that the polydactyly observed here has a genetic background.

Although congenital digital defects, particularly polydactyly, have been reported frequently in humans, their occurrence in rhesus macaques is relatively rare. We observed two cases of spontaneous digital defects in male rhesus monkey infants recently born at the California Regional Primate Research Center. One infant exhibited bilateral postaxial polydactyly and the other infant had bilateral oligodactyly with unilateral phalangeal duplication. In this report, we present the clinical/pathological details of these cases as well as discuss the embryology of normal and abnormal limb development. We will also summarize a variety of spontaneous and experimentally induced digital defects that have been reported in several nonhuman primate species.

In 1995, the discovery of leg malformations in several screech owl (Otis asio) nestlings and in their female parent at a Department of Energy (DOE) Superfund site in South Carolina prompted an investigation into the nature of the observed abnormalities. Surviving nestlings and the female parent were transferred to a captive screech owl breeding colony at the USGS Patuxent Wildlife Research Center, Laurel, MD. The malformed female parent and her offspring were each mated with normal owls from the colony for 3 yr. Matings of the malfored female produced five malformed and six normal owls; all owls produced by matings of normal offspring were normal. Malformed offspring were euthanized when it became apparent that their physical distress precluded survival under normal conditions of colony care. Euthanized owls were necropsied and examined for skeletal development. Detailed descriptions of eight malformed owls are presented. Results of the matings indicated that the leg mafformations were caused by a genetic trait in the female parent that was heterozygous dominant. The characteristic was lethal except in occasional mild manifestations and resembled an extreme form of a dominant abnormality previously described for domestic fowl called duplicate polydactyly. Other reports of skeletal abnormalities in wild birds and potential environmental causes of genetic mutations at the DOE Superfund site are presented. Other studies performed at the DOE Superfund site do not implicate elevated (above background) ionizing radiation from 137Cs, the dominant radionuclide where the owls were captured, as the cause of the mutation. The cause of this genetic abnormality remains unknown.

A 2-mo-old, 90-kg, intact male camel (Camelus dromedarius) was admitted for surgical removal of a supernumerary digit associated with the medial aspect of the right carpus and metacarpus. Radiographic views of the carpus and metacarpus revealed the supernumerary digit articulating with the middle carpal joint via an extra carpal bone. The supernumerary digit consisted of three bones. Surgical removal of the supernumerary digit was recommended to restore normal limb conformation, limit the possibility of future lameness, and improve the cosmetic appearance of the limb. Complete surgical removal of the digit was performed by disarticulating the extra carpal bone from its attachments to the second and radial carpal bones. One year after surgery, the leg appeared grossly normal and the camel showed no sign of lameness.

A presumed genetic syndrome is described in a family of St. Bernards. Four identically affected littermates presented the association of palate agenesis, anotia, incomplete bifid tongue, preaxial hind paw polydactyly, and an extra thoracic vertebra and rib. Pedigree analysis is compatible with an autosomal recessive gene.

Eleven cases of congenital anomalies were identified in 210 (5%) juvenile northern elephant seals (Mirounga angustirostris) found stranded along the central California (USA) coast from 1 January 1988 to 31 December 1995. Seven individuals had mild-to-moderate hydrocephalus involving the lateral ventricles bilaterally, or the lateral and third ventricles. Two animals had severe cardiac anomalies: hypoplasia of the right ventricle with overriding aorta, and ventricular septal defect. Other anomalies included single cases of hydronephrosis, focal pulmonary dysplasia, and congenital epidermal angiomatosis. Common intercurrent disease processes were verminous pneumonia and arteritis, verminous enteritis and coliti, and splenic and hepatic hemosiderosis. The more severe anomalies were considered to be the cause of debilitation and stranding. Milder anomalies were found incidentally during routine gross necropsy and histopathologic examination.

Polydactylism, an excess deformity in a foal is described. The hereditary pathology and etiopathogenesis are discussed. A method of surgical correction of the deformed extremity is introduced. Indication and prognosis of the surgical correction of polydactylism and aspects concerning the breeding management are discussed.