Advances in the molecular genetics of non-syndromic polydactyly

Two Novel Frameshift Mutations in the GLI3 Gene Underlie Non-Syndromic Polydactyly in Chinese Families

Objective: Polydactyly is characterized by multiple distinct heterogeneous phenotypes, the etiologies of which involve several genes. This study aimed to explore the genetic defects and further clarify the molecular mechanism of polydactyly in several Chinese families. Methods: Three families with diverse phenotypes of non-syndromic polydactyly were analyzed: two were cases of familial disease, whereas one was sporadic. PCR and Sanger sequencing were used to screen for pathogenic mutations in two known disease-associated genes, GLI3 and HOXD13, while bioinformatic analyses predicted the pathogenicity of the identified variants. Reverse transcription PCR was used to analyze the splicing effect of an intronic variant. Results: Two novel heterozygous frameshift mutations (c.4478delG/p.S1493Tfs*18; c.846_c.847insC/p.R283Qfs*21) were identified in the GLI3 gene from two of the pedigrees. Both c.4478delG and c.846_c.847insC were later confirmed in affected and unaffected members and normal controls, to truncate and disrupt the integrity of the GLI3 protein, reduce its level of expression, and disrupt its biological function through nonsense-mediated mRNA decay (NMD). In addition, a deep intron mutation (c.125-47 C>A) was detected in the GLI3 gene from the sporadic case, however, both bioinformatics analysis (HSF, splice AI, and CBS) and RT-PCR indicated that the variant c.125-47 C>A had minimal if any impact on splicing of the GLI3 gene. Conclusion: Two newly identified heterozygous frameshift mutations in the GLI3 gene were detected in two families with non-syndromic polydactyly, further extending the mutational spectrum of the GLI3 gene in non-syndromic polydactyly. Moreover, our study further expanded the phenotypic spectrum of non-syndromic polydactyly.

A Rare Combination of Heptadactyl and Hexadactyl Polydactyly in a Neonate

Heptadactyly and hexadactyly are rare congenital disorders from the polydactyly family. This type of polydactyly is usually classified into three major groups: preaxial (medial ray), postaxial (lateral ray), and central polydactyly. The most common presentation is both preaxial and postaxial polydactyly. The occurrence of heptadactyly and hexadactyly has been reported but the presence of both in the same infant has not been reported yet. We report the presence of both these abnormalities in the same infant.

Polydactyly: Clinical and molecular manifestations

Polydactyly is a malformation during the development of the human limb, which is characterized by the presence of more than the normal number of fingers or toes. It is considered to be one of the most common inherited hand disorders. It can be divided into two major groups: Non-syndromic polydactyly or syndromic polydactyly. According to the anatomical location of the duplicated digits, polydactyly can be generally subdivided into pre-, post-axial, and mesoaxial forms. Non-syndromic polydactyly is often inherited with an autosomal dominant trait and defects during the procedure of anterior-posterior patterning of limb development are incriminated for the final phenotype of the malformation. There are several forms of polydactyly, including hand and foot extra digit manifestations. The deformity affects upper limbs with a higher frequency than the lower, and the left foot is more often involved than the right. The treatment is always surgical. Since the clinical presentation is highly diverse, the treatment combines single or multiple surgical operations, depending on the type of polydactyly. The research attention that congenital limb deformities have recently attracted has resulted in broadening the list of isolated gene mutations associated with the disorders. Next generation sequencing technologies have contributed to the correlation of phenotype and genetic profile of the multiple polydactyly manifestations and have helped in early diagnosis and screening of most non-syndromic and syndromic disorders.

A review of polydactyly and its inheritance: Connecting the dots

OBJECTIVE

This study collects what is known about the inheritance underpinnings of syndromic and non-syndromic polydactylies and highlights dactyly presentations with unknown genetic roots. This review summarizes the current information and genetics-enhanced understanding of polydactyly.

BACKGROUND

There is a frequency of 0.37 to 1.2 per 1000 live births for polydactyly, which is also known as hyperdactyly. It is characterized by the presence of extra fingers. Polydactyly is caused by a failure in limb development, specifically the patterning of the developing limb bud. The phenotypic and genetic variability of polydactyly makes its etiology difficult to understand. Pre-axial polydactyly, central polydactyly (axial), and postaxial polydactyly are all examples of non-syndromic polydactyly (ulnar). An autosomal dominant disorder with varying penetrance that is mostly passed down via limb development patterning abnormalities.

METHOD

A comprehensive search of MEDLINE/PubMed and other databases was followed by an evaluation of the relevant papers, with a particular focus on those published between 2000 and 2022.

RESULTS

Of 747 published article related to Polydactyly from MEDLINE/PubMed search, 43 were from the last 10 years and were the focus of this review.

CONCLUSION

Polydactyly is one of the most frequent congenital hand malformations. PAP is more common than PPD, whereas central polydactyly is very uncommon.

The molecular genetics of human appendicular skeleton

Disorders that result from de-arrangement of growth, development and/or differentiation of the appendages (limbs and digit) are collectively called as inherited abnormalities of human appendicular skeleton. The bones of appendicular skeleton have central role in locomotion and movement. The different types of appendicular skeletal abnormalities are well described in the report of "Nosology and Classification of Genetic skeletal disorders: 2019 Revision". In the current article, we intend to present the embryology, developmental pathways, disorders and the molecular genetics of the appendicular skeletal malformations. We mainly focused on the polydactyly, syndactyly, brachydactyly, split-hand-foot malformation and clubfoot disorders. To our knowledge, only nine genes of polydactyly, five genes of split-hand-foot malformation, nine genes for syndactyly, eight genes for brachydactyly and only single gene for clubfoot have been identified to be involved in disease pathophysiology. The current molecular genetic data will help life sciences researchers working on the rare skeletal disorders. Moreover, the aim of present systematic review is to gather the published knowledge on molecular genetics of appendicular skeleton, which would help in genetic counseling and molecular diagnosis.

GLIS Family Zinc Finger 1 was First Linked With Preaxial Polydactyly I in Humans by Stepwise Genetic Analysis

Background: Preaxial polydactyly (PPD) is one of the most common developmental malformations, with a prevalence of 0.8–1.4% in Asians. PPD is divided into four types, PPD I–IV, and PPD I is the most frequent type. Only six loci (GLI1, GLI3, STKLD1, ZRS, pre-ZRS, and a deletion located 240 kb from SHH) have been identified in non-syndromic PPD cases. However, pathogenesis of most PPD patients has never been investigated. This study aimed to understand the genetic mechanisms involved in the etiology of PPD I in a family with multiple affected members.

Methods: We recruited a PPD I family (PPD001) and used stepwise genetic analysis to determine the genetic etiology. In addition, for functional validation of the identified GLIS1 variant, in vitro studies were conducted. GLIS1 variants were further screened in additional 155 PPD cases.

Results: We identified a GLIS1 variant (NM_147193: c.1061G > A, p.R354H) in the PPD001 family. In vitro studies showed that this variant decreased the nuclear translocation of GLIS1 and resulted in increased cell viability and migration. RNA sequencing revealed abnormal TBX4 and SFRP2 expression in 293T cells transfected with mutant GLIS1. Additionally, we identified a GLIS1 variant (c.664G > A, p.D222N) in another PPD case.

Conclusion: We identified two GLIS1 variants in PPD I patients and first linked GLIS1 with PPD I. Our findings contributed to future molecular and clinical diagnosis of PPD and deepened our knowledge of this disease.

A Novel Missense Variant of HOXD13 Caused Atypical Synpolydactyly by Impairing the Downstream Gene Expression and Literature Review for Genotype-Phenotype Correlations

Synpolydactyly (SPD) is a hereditary congenital limb malformation with distinct syndactyly designated as SPD1, SPD2, and SPD3. SPD1 is caused by mutations of HOXD13, which is a homeobox transcription factor crucial for limb development. More than 143 SPD patients have been reported to carry HOXD13 mutations, but there is a lack of genotype-phenotype correlation. We report a novel missense mutation of c. 925A > T (p.I309F) in an individual with atypical synpolydactyly inherited from her father with mild clinodactyly and three other different alanine insertion mutations in HOXD13 identified by whole exome sequencing (WES) in 12 Chinese SPD families. Unlike polyalanine extension, which tends to form α-helix and causes protein aggregation in the cytoplasm as shown by molecular simulation and immunofluorescence, the c. 925A > T mutation impairs downstream transcription of EPHA7. We compiled literature findings and analyzed genotype-phenotype features in 173 SPD individuals of 53 families, including 12 newly identified families. Among the HOXD13-related individuals, mutations were distributed in three regions: polyalanine, homeobox, and non-homeobox. Polyalanine extension was the most common variant (45%), followed by missense mutations (32%) mostly in the homeobox compared with the loss-of-function (LOF) variants more likely in non-homeobox. Furthermore, a more severe degree and classic SPD were associated with polyalanine mutations although missense variants were associated with brachydactyly and syndactyly in hands and feet and LOF variants with clinodactyly in hands. Our study broadens the HOXD13 mutation spectrum and reveals the profile of three different variants and their severity of SPD, the genotype-phenotype correlation related to the HOXD13 mutation site provides clinical insight, including for genetic counseling.

OFD Type I syndrome: lessons learned from a rare ciliopathy

The OFD1 gene was initially identified as the gene responsible for the X-linked dominant male lethal OFD type I syndrome, a developmental disorder ascribed to cilia disfunction. The transcript has been subsequently associated to four different X-linked recessive conditions, namely Joubert syndrome, retinitis pigmentosa, primary ciliary dyskinesia and Simpson-Golabi-Behmel type 2 syndrome. The centrosomal/basal body OFD1 protein has indeed been shown to be required for primary cilia formation and left-right asymmetry. The protein is also involved in other tasks, e.g. regulation of cellular protein content, constrain of the centriolar length, chromatin remodeling at DNA double strand breaks, control of protein quality balance and cell cycle progression, which might be mediated by non-ciliary activities. OFD1 represents a paradigmatic model of a protein that performs its diverse actions according to the cell needs and depending on the subcellular localization, the cell type/tissue and other possible factors still to be determined. An increased number of multitask protein, such as OFD1, may represent a partial explanation to human complexity, as compared with less complex organisms with an equal or slightly lower number of proteins.

When Is Primary Metacarpal Corrective Osteotomy Recommended in Patients with Flatt Type IV Radial Polydactyly?

BACKGROUND

The aim of this study was to determine when primary metacarpal corrective osteotomy is recommended in patients with Flatt type IV radial polydactyly.

METHODS

A total of 78 patients with Flatt type IV radial polydactyly were included. The authors performed metacarpal osteotomy if the angulation of the metacarpophalangeal joint was not correctable by the intraoperative radial stress test. The authors measured the metacarpal deviation angle of the thumb in simple posteroanterior radiographs. The clinical outcomes were assessed using Japanese Society for Surgery of the Hand evaluation total score and the metacarpal deviation angle correction angle. These outcomes were compared between the patients who underwent metacarpal osteotomy and those who did not. Of the patients who did not undergo metacarpal osteotomy, the relationships between preoperative metacarpal deviation angle and the metacarpal deviation angle correction angle were formulated using segmented linear regression analysis.

RESULTS

There were no significant differences in the demographic features and the value of preoperative metacarpal deviation angle between the two groups. However, the metacarpal deviation angle correction angle and Japanese Society for Surgery of the Hand evaluation total score were significantly higher in the patients who underwent metacarpal osteotomy. The segmented linear regression analysis demonstrated a breakpoint, indicating that the soft-tissue procedure alone does not sufficiently correct the metacarpal deviation angle. For the postoperative metacarpal deviation angle to be 5 degrees, the preoperative metacarpal deviation angle was calculated as 10.8 degrees.

CONCLUSION

If the preoperative metacarpal deviation angle is greater than 10.8 degrees, metacarpal osteotomy can be considered even in patients with correctable metacarpophalangeal joint by intraoperative radial stress test.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, III.

Identification of the genetic basis of sporadic polydactyly in China by targeted sequencing

Purpose

Polydactyly is a highly heterogeneous group of skeletal deformities in clinical and genetic background. The variation spectrum in Chinese sporadic polydactyly has not been comprehensively analyzed. To elucidate genetic variation spectrum and genotype-phenotype correlations in Chinese patients with polydactyly, we conducted comprehensive genetic analysis of patients nationwide using targeted sequencing.

Methods

A total of 181 patients diagnosed with polydactylies were recruited. We designed a targeted capture panel for sequencing 721 genes that are associated with the pathogenesis of skeletal dysplasia. We performed rigorous variant- and gene-level filtrations to identify potentially damaging variants, followed by enrichment analysis and gene prioritization.

Results

A total of 568 deleterious variants of 293 genes were identified in 173 of 181 patients with a positive rate of 95.6% by targeted sequencing. For each sample, an average of 3.17 deleterious variants were identified. Especially, 14 pathogenic or likely pathogenic variants were identified in 10 genes in 14 patients out of the 181 patients, providing a positive molecular diagnostic rate of 7.7%.

Conclusion

Targeted sequencing analysis provides a high efficiency approach for the genetic diagnosis of polydactyly. This is the largest next generation sequencing study performed to date in patients with polydactyly and represents the genetic basis of polydactyly typically encountered in genetics clinics.

Polydactyly Patient Carried a Mutation of PTCH1 Which Has Been Identified in Nevoid Basal Cell Nevus Syndrome

Polydactyly frequently exhibits autosomal dominant inheritance, which is characterized by supernumerary fingers or toes. The growth of the limb was controlled by three signaling pathways in three-dimensional axis. Sonic Hedgehog signaling, which controls the anterior to posterior (radial to ulnar) orientation has been suspected to be a main cause for polydactyly. To determine the pathogenesis of the patients with polydactyly, we recruited a polydactyly family with two patients. Taking advantage of next-generation sequencing technology, we applied whole-exome sequencing and Sanger sequencing to the proband and her daughter. The analysis of the whole-exome sequencing showed a heterozygous missense mutation c.3617G>A (p.R1206H) in the PTCH1 gene. The results of Sanger sequencing also verified this mutation. Our research discovered a candidate gene of polydactyly-PTCH1. We are the first to point out the relationship between polydactyly and PTCH1 mutation in human. As the PTCH1 gene mutations have been identified in nevoid basal cell nevus syndrome (NBCCS), and polydactyly is one phenotype of NBCCS, it may provide a new clue to the study of the genotype-phenotype correlations between the PTCH1 gene mutations and NBCCS.

Novel GLI3 Mutations in Chinese Patients with Non-syndromic Post-axial Polydactyly

BACKGROUND

Polydactyly, characterized by supernumerary digits in the upper or lower extremities, is the most common congenital digital abnormalities. It derives from the defective patterning of anteroposterior axis of the developing limb, with various etiology and clinical heterogeneity. The patients with post-axial polydactyly type A (PAPA) have the typical symptom of a well-formed supernumerary digit outside the fifth digit.

OBJECTIVE

The aim of present study was to identify the causative mutations of two unrelated Han Chinese patients with non-syndromic PAPA.

METHODS

Two unrelated Han Chinese patients and 100 ethnicity-matched, unrelated normal controls were recruited for this study. BGISEQ-500 exome sequencing was performed in the two patients, followed by validation in the patients and 100 controls by using Sanger sequencing.

RESULTS

Two mutations in the GLI family zinc finger 3 gene (GLI3), including a frameshift mutation c.3437_3453delTCGAGCAGCCCTGCCCC (p.L1146RfsX95) and a nonsense mutation c.3997C>T (p.Q1333X), were identified in two patients but were absent in the 100 healthy controls.

CONCLUSION

The two GLI3 mutations, p.L1146RfsX95 and p.Q1333X, may account for non-syndromic PAPA in the two patients, respectively. The findings of this study may expand the mutational spectrum of GLI3-PAPA and provide novel insights into the genetic basis of polydactyly.

A Novel Frameshift Mutation of GLI3 Causes Isolated Postaxial Polydactyly

BACKGROUND

GLI3 encodes a transcription factor in the sonic hedgehog signaling pathway, which is essential in regulating the human limb bud development, especially on the anteroposterior axis. Mutations in GLI3 have been confirmed to be associated with various human congenital malformations, including Greig cephalopolysyndactyly syndrome, Pallister-Hall syndrome, and isolated polydactyly. A robust gene-phenotype relationship between GLI3 and Greig cephalopolysyndactyly syndrome and Pallister-Hall syndrome has been well elucidated, and less is known about GLI3 mutation-caused isolated polydactyly. This study intended to perform a mutation analysis of GLl3 in a family with isolated polydactyly.

METHODS

A 3-generation Chinese family with 19 members was recruited in this study, of which the proband and her mother were affected with polydactyly. The whole-exon sequencing was performed to find mutations, and Sanger sequencing was performed to validate the mutations.

RESULTS

We found a novel heterozygous frameshift mutation of GLI3 (c.1180C > TT, p.P394fs18x) in the proband of a Chinese family with isolated postaxial polydactyly. No mutation was detected in the proband's father or another 2 patients with sporadic preaxial polydactyly.

CONCLUSIONS

By systematically reviewing the gene-phenotype relationship, we found that GLI3 p.P394fs18x mutation might be specific for isolated postaxial polydactyly.

Mutational Screening of GLI3, SHH, and SHH ZRS in 78 Chinese Children with Nonsyndromic Polydactyly

BACKGROUND

Polydactyly is one of the most common congenital limb abnormalities. Our objective was to identify the genetic causes of non-syndromic polydactyly in 78 Chinese children.

MATERIALS AND METHODS

Genomic DNA was isolated from 78 independent nonsyndromic polydactyly patients, of whom 71 had preaxial polydactyly (PPD), six had postaxial polydactyly (PAP), and one showed combined PPD1 and PAP-A/B. The coding areas and exon/intron boundaries of the GLI3 and SHH genes and the genomic region of SHH ZRS were amplified by polymerase chain reaction and sequenced.

RESULTS

The patient with combined PPD1 and PAP-A/B (subject DUO36) exhibited a heterozygous nonsense mutation in chr7: 42004164G>A (ENST00000395925, c.4507C>T, p.Gln1503Stop ) of the GLI3 gene that has not been previously recorded. We did not detect any mutations in GLI3, SHH, or SHH ZRS in the other 77 nonsyndromic polydactyly patients.

CONCLUSION

The novel mutation in GLI3 c.4507C>T is likely one of the causes of the PAP and PPD1 of subject DUO36. This important finding should facilitate the optimization of genetic testing for nonsyndromic polydactyly.

Clinical Genetics of Polydactyly: An Updated Review

Polydactyly, also known as hyperdactyly or hexadactyly is the most common hereditary limb anomaly characterized by extra fingers or toes, with various associated morphologic phenotypes as part of a syndrome (syndromic polydactyly) or may occur as a separate event (non-syndromic polydactyly). Broadly, the non-syndromic polydactyly has been classified into three types, i.e.; preaxial polydactyly (radial), central polydactyly (axial), and postaxial polydactyly (ulnar). Mostly inherited as an autosomal dominant entity with variable penetrance and caused by defects that occur in the anterior-posterior patterning of limb development. In humans, to-date at least 10 loci and six genes causing non-syndromic polydactyly have been identified, including the ZNF141, GLI3, MIPOL1, IQCE, PITX1, and the GLI1. In the present review, clinical, genetic and molecular characterization of the polydactyly types has been presented including the recent genes and loci identified for non-syndromic polydactyly. This review provides an overview of the complex genetic mechanism underlie polydactyly and might help in genetic counseling and quick molecular diagnosis.

A loss-of-function homozygous mutation in DDX59 implicates a conserved DEAD-box RNA helicase in nervous system development and function

We report on a homozygous frameshift deletion in DDX59 (c.185del: p.Phe62fs*13) in a family presenting with orofaciodigital syndrome phenotype associated with a broad neurological involvement characterized by microcephaly, intellectual disability, epilepsy, and white matter signal abnormalities associated with cortical and subcortical ischemic events. DDX59 encodes a DEAD‐box RNA helicase and its role in brain function and neurological diseases is unclear. We showed a reduction of mutant cDNA and perturbation of SHH signaling from patient‐derived cell lines; furthermore, analysis of human brain gene expression provides evidence that DDX59 is enriched in oligodendrocytes and might act within pathways of leukoencephalopathies‐associated genes. We also characterized the neuronal phenotype of the Drosophila model using mutant mahe, the homolog of human DDX59, and showed that mahe loss‐of‐function mutant embryos exhibit impaired development of peripheral and central nervous system. Taken together, our results support a conserved role of this DEAD‐box RNA helicase in neurological function.

Genetic Overview of Syndactyly and Polydactyly

Syndactyly and polydactyly-respectively characterized by fused and supernumerary digits-are among the most common congenital limb malformations, with syndactyly presenting at an estimated incidence of 1 in 2,000-3,000 live births and polydactyly at a frequency of 1 in approximately 700-1,000 live births. Despite their relatively regular manifestation in the clinic, the etiologies of syndactyly and polydactyly remain poorly understood because of their phenotypic and genetic diversity. Further, even though concrete knowledge of genotypic links has been established for some variants of syndactyly and polydactyly, there appears to be no single comprehensive published summary of all syndromic and nonsyndromic syndactyly and polydactyly presentations, and there is decidedly no resource that maps all syndromic and nonsyndromic syndactylies and polydactylies to their genetic bases. This gap in the literature problematizes comprehensive carrier screening and prenatal diagnosis and complicates novel diagnostic attempts. This review thus attempts to collect all that is known about the genetic bases of syndromic and nonsyndromic syndactylies and polydactylies, as well as to highlight the dactyly manifestations for which no genetic bases are as yet known. Then, having established a summation of existing and missing knowledge, this work briefly outlines the diagnostic techniques that a genetics-reinforced understanding of syndactyly and polydactyly could inform.

Disentangling Timing of Admixture, Patterns of Introgression, and Phenotypic Indicators in a Hybridizing Wolf Population

Hybridization is a natural or anthropogenic process that can deeply affect the genetic make-up of populations, possibly decreasing individual fitness but sometimes favoring local adaptations. The population of Italian wolves (Canis lupus), after protracted demographic declines and isolation, is currently expanding in anthropic areas, with documented cases of hybridization with stray domestic dogs. However, identifying admixture patterns in deeply introgressed populations is far from trivial. In this study, we used a panel of 170,000 SNPs analyzed with multivariate, Bayesian and local ancestry reconstruction methods to identify hybrids, estimate their ancestry proportions and timing since admixture. Moreover, we carried out preliminary genotype-phenotype association analyses to identify the genetic bases of three phenotypic traits (black coat, white claws, and spur on the hind legs) putative indicators of hybridization. Results showed no sharp subdivisions between nonadmixed wolves and hybrids, indicating that recurrent hybridization and deep introgression might have started mostly at the beginning of the population reexpansion. In hybrids, we identified a number of genomic regions with excess of ancestry in one of the parental populations, and regions with excess or resistance to introgression compared with neutral expectations. The three morphological traits showed significant genotype-phenotype associations, with a single genomic region for black coats and white claws, and with multiple genomic regions for the spur. In all cases the associated haplotypes were likely derived from dogs. In conclusion, we show that the use of multiple genome-wide ancestry reconstructions allows clarifying the admixture dynamics even in highly introgressed populations, and supports their conservation management.

Exome sequencing revealed a splice site variant in the IQCE gene underlying post-axial polydactyly type A restricted to lower limb

Polydactyly is characterized by an extra supernumerary digit/toe with or without bony element. To date variants in four genes GLI3, ZNF141, MIPOL1 and PITX1 have been implicated in developing non-syndromic form of polydactyly. The present study involved characterization of large consanguineous family of Pakistani origin segregating post-axial polydactyly type A, restricted to lower limb, in autosomal recessive pattern. DNA of two affected members in the family was subjected to exome sequencing. Sanger sequencing was then followed to validate segregation of the variants in the family members. A homozygous splice acceptor site variant (c.395-1G>A) was identified in the IQCE gene, which completely co-segregated with post-axial polydactyly phenotype within the family. The homozygous variant was absent in different public variant databases, 7000 in-house exomes, 130 exomes from unrelated Pakistani individuals and 215 ethnically matched controls. Mini-gene splicing assay was used to test effect of the variant on function of the gene. The assay revealed loss of first nucleotide of exon 6, producing a -1 frameshift and a premature stop codon 22 bases downstream of the variant (p.Gly132Valfs*22). The study provided the first evidence of involvement of the IQCE gene in limbs development in humans.

Mutational screening of GLI3, SHH, preZRS, and ZRS in 102 Chinese children with nonsyndromic polydactyly

BACKGROUND

Polydactyly is a group of congenital limb malformations that show high degree of phenotypic variability and genetic heterogeneity.

RESULTS

In the present study, four genomic regions (exons of GLI3, SHH, and noncoding sequences of preZRS and ZRS) involved in hedgehog (Hh) signaling pathway were sequenced for 102 unrelated Chinese children with nonsyndromic polydactyly. Two GLI3 variants (c.2844 G > G/A; c.1486C > C/T) and four preZRS variants (chr7:156585336 A>G; chr7:156585421 C>A; chr7: 156585247 G>C; chr7:156585420 A > C) were observed in 2(2.0%) and 6(5.9%) patients, respectively. These variants are not over-represented in the Chinese healthy population. All the 8 cases showed preaxial polydactyly in hands. Additionally, no specific patterns of malformation predicted mutations in other candidate genes or sequences.

CONCLUSIONS

This is the first report of the assessment of the frequency of GLI3/SHH/preZRS/ZRS in Chinese patients to show any higher possibility of mutations or variants for the 4 genes or sequences in China. Developmental Dynamics 246:392-402, 2017. © 2017 Wiley Periodicals, Inc.