Polydactyly: phenotypes, genetics and classification

Congenital three generation wide familial non-syndromic polydactyly

Polydactyly is typically observed as isolated and sporadic occurrences, although familial cases do exist, albeit with lower frequency, manifesting in various inheritance patterns. In around 30% of polydactyly cases, there exists a familial history, suggesting the probable involvement of a single gene. Given its potential for hereditary transmission, thorough investigation of the patients' parents, first-degree relatives, grandparents, and even great-grandparents for similar disorders becomes imperative. In our clinic, we conducted an analysis focusing on patients presenting with foot polydactyly, along with occurrences of polydactyly among their first- and second-degree relatives spanning two to three generations of family history. The study encompassed three patients and their respective families, including a pair of siblings. We speculate that the inheritance type in our cases was autosomal dominant. Among our patients, one presented with central polydactyly, while the remaining patients and all familial cases displayed postaxial polydactyly. In terms of morphologic classification, one patient had a Y-shaped metatarsal, another had a T-shaped metatarsal, and the third patient exhibited a duplicated ray-shaped anomaly. In our review of the literature, we haven't come across a case spanning three generations like the ones we encountered. Additionally, the presence of a transverse accessory extensor tendon between both extensor tendons in cases with T- and Y-shaped metatarsals intrigued us from an anatomical perspective. Our goal is to present these rare cases of congenital familial polydactyly spanning three generations, highlighting the anatomical variations observed and aiming to contribute to the existing body of literature on the subject.

A novel GLI3 frameshift mutation in a Chinese pedigree with polydactyly: A case report

Background

GLI3 gene mutations can result in various forms of polysyndactyly, such as Greig cephalopolysyndactyly syndrome (GCPS, MIM: #175700), Pallister-Hall syndrome (PHS, MIM: #146510), and isolated polydactyly (IPD, MIM: #174200, #174700). Reports on IPD-associated GLI3 mutations are rare. In this study, a novel GLI3 mutation was identified in a Chinese family with IPD.

Results

We report a family with six members affected by IPD. The family members demonstrated several special phenotypes, including sex differences, abnormal finger joint development, and different polydactyly types. We identified a novel frameshift variant in the GLI3 gene (NM_000168.6: c.1820_1821del, NP_000159.3: p.Tyr607Cysfs*9) by whole-exome sequencing. Further analysis suggested that this mutation was the cause of polydactyly in this family.

Conclusions

The discovery of this novel frameshift variant in our study further solidifies the relationship between IPD and GLI3 and expands the previously established spectrum of GLI3 mutations and associated phenotypes.

Epidemiology of congenital polydactyly and syndactyly in Hunan Province, China

OBJECTIVE

To describe the prevalence and epidemiology of congenital polydactyly and syndactyly in Hunan Province, China, 2016-2020.

METHODS

Data were obtained from the Birth Defects Surveillance System in Hunan Province, China, 2016-2020. Prevalence of birth defects (polydactyly or syndactyly) is the number of cases per 1000 births (unit: ‰). Prevalence and 95% confidence intervals (CI) were calculated by the log-binomial method. Chi-square trend tests (χ2trend) were used to determine trends in prevalence by year. Crude odds ratios (ORs) were calculated to examine the association of each demographic characteristic with polydactyly and syndactyly.

RESULTS

Our study included 847,755 births, and 14,459 birth defects were identified, including 1,888 polydactyly and 626 syndactyly cases, accounting for 13.06% and 4.33% of birth defects, respectively. The prevalences of total birth defects, polydactyly, and syndactyly were 17.06‰ (95%CI: 16.78-17.33), 2.23‰ (95%CI: 2.13-2.33), and 0.74‰ (95%CI: 0.68-0.80), respectively. Most polydactyly (96.77%) and syndactyly (95.69%) were diagnosed postnatally (within 7 days). From 2016 to 2020, the prevalences of polydactyly were 1.94‰, 2.07‰, 2.20‰, 2.54‰, and 2.48‰, respectively, showing an upward trend (χ2trend = 19.48, P < 0.01); The prevalences of syndactyly were 0.62‰, 0.66‰, 0.77‰, 0.81‰, and 0.89‰, respectively, showing an upward trend (χ2trend = 10.81, P = 0.03). Hand polydactyly (2.26‰ vs. 1.33‰, OR = 1.69, 95%CI: 1.52-1.87) and hand syndactyly (0.43‰ vs. 0.28‰, OR = 1.42, 95%CI: 1.14-1.76) were more common in males than females. Polydactyly (2.67‰ vs. 1.93‰, OR = 1.38, 95%CI: 1.26-1.51) and syndactyly (0.91‰ vs. 0.62‰, OR = 1.47, 95%CI: 1.26-1.72) were more common in urban areas than in rural areas. Compared to maternal age 25-29, hand polydactyly was more common in maternal age < 20 (2.48‰ vs. 1.74‰, OR = 1.43, 95%CI: 1.01-2.02) or ≥ 35 (2.25‰ vs. 1.74‰, OR = 1.30, 95%CI: 1.12-1.50).

CONCLUSION

In summary, we have described the prevalence and epidemiology of polydactyly and syndactyly from hospital-based surveillance in Hunan Province, China, 2016-2020. Our findings make some original contributions to the field, which may be valuable for future research.

A case-control study characterizing polydactyly risk factors in Bogotá and Cali, Colombia between 2002 and 2020

BACKGROUND

Polydactyly is a congenital abnormality characterized by the presence of additional fingers on one or more extremities. In Colombia, polydactyly accounted for 17% of musculoskeletal congenital abnormalities in 2021, with a prevalence of 6.03 per 10,000 live births. The purpose of this study was to determine the prevalence of polydactyly and identify associated risk factors in Bogotá and Cali, Colombia, from 2002 to 2020.

METHODS

A retrospective case-control study design was employed, analyzing data from birth defect reports provided by the Program for the Prevention and Follow-up of Congenital Defects and Orphan Diseases surveillance system. Cases included live births or stillbirths with polydactyly, while controls consisted of infants without congenital abnormality, matched in terms of birth date and hospital. Prevalence of polydactyly was calculated and risk factors were assessed through odds ratios obtained by logistic regression models, considering a 95% confidence interval.

RESULTS

Among the 558,255 births included in the study, 848 cases of polydactyly were identified, resulting in a prevalence rate of 15.19 per 10,000 live births. Risk factors associated with polydactyly included male newborn sex, pregestational diabetes, and a family history of malformation among first-degree relatives.

CONCLUSION

These findings highlight the importance a surveillance system aimed to characterize populations with congenital abnormalities, providing a better option for analyzing risk factors, help improving prevention, diagnosis, notification, and optimal treatment in patients.

Brachyolmia, dental anomalies and short stature (DASS): Phenotype and genotype analyses of Egyptian and Pakistani patients

Brachyolmia is a heterogeneous group of developmental disorders characterized by a short trunk, short stature, scoliosis, and generalized platyspondyly without significant deformities in the long bones. DASS (Dental Abnormalities and Short Stature), caused by alterations in the LTBP3 gene, was previously considered as a subtype of brachyolmia. The present study investigated three unrelated consanguineous families (A, B, C) with Brachyolmia and DASS from Egypt and Pakistan. In our Egyptian patients, we also observed hearing impairment. Exome sequencing was performed to determine the genetic causes of the diverse clinical conditions in the patients. Exome sequencing identified a novel homozygous splice acceptor site variant (LTBP3:c.3629-1G > T; p. ?) responsible for DASS phenotypes and a known homozygous missense variant (CABP2: c.590T > C; p.Ile197Thr) causing hearing impairment in the Egyptian patients. In addition, two previously reported homozygous frameshift variants (LTBP3:c.132delG; p.Pro45Argfs*25) and (LTBP3:c.2216delG; p.Gly739Alafs*7) were identified in Pakistani patients. This study emphasizes the vital role of LTBP3 in the axial skeleton and tooth morphogenesis and expands the mutational spectrum of LTBP3. We are reporting LTBP3 variants in seven patients of three families, majorly causing brachyolmia with dental and cardiac anomalies. Skeletal assessment documented short webbed neck, broad chest, evidences of mild long bones involvement, short distal phalanges, pes planus and osteopenic bone texture as additional associated findings expanding the clinical phenotype of DASS. The current study reveals that the hearing impairment phenotype in Egyptian patients of family A has a separate transmission mechanism independent of LTBP3.

Paternal age and risk for selected birth defects in a large South American sample

BACKGROUND

The relationship between maternal age (MA) and birth defects (BD) has been extensively studied while much less research, mostly with discordant results, has focused on the risk of paternal age (PA) for BD. Furthermore, no consensus has been reached on the best way to control the association of PA with MA.

OBJECTIVES

The aim of the study was to evaluate the risk of PA increase, at 1-year intervals, for selected BD, especially controlling for the confounding effect of MA.

METHODS

The sample comprised of 27,944 liveborns presenting 1 of 18 selected isolated BD. Conditional logistic regressions were applied to evaluate the risk of advanced PA and its yearly increase, adjusting by MA and other variables.

RESULTS

Of the 18 analyzed BD, only the risk for preaxial polydactyly (PreP) showed a significant association with increasing PA, while advanced MA was of low risk. For esophageal and anal atresia, associations with both PA and MA increases were observed.

CONCLUSIONS

Results support the hypothesis of advanced PA as a risk factor for PreP and helps clarify the so far unexplained nonrandom association between this defect and Down syndrome.

Unusual Presentation of Familial Unilateral Postaxial Polydactyly With Metacarpal Delta Phalanx: A Report of a Rare Case

The term "delta phalanx" is proposed to characterize an uncommon deformity that typically affects the middle phalanx of a finger. It has the appearance of the Greek capital letter delta, meaning it is shaped like a triangle. Because the faulty epiphysis occurs proximally to distally instead of along its usual horizontal course, the bone has a semilunar shape. Functional impairment or significant finger shortening are indications for surgery. A variety of congenital hand anomalies are linked to the delta phalanx. Few cases of middle delta phalanx in the ulnar polydactyly finger have been documented. This case study investigates an extremely uncommon occurrence of metacarpal delta phalanx in an ulnar polydactyly finger.

Hyperplastic Human Macromass Cartilage for Joint Regeneration

Cartilage damage affects millions of people worldwide. Tissue engineering strategies hold the promise to provide off-the-shelf cartilage analogs for tissue transplantation in cartilage repair. However, current strategies hardly generate sufficient grafts, as tissues cannot maintain size growth and cartilaginous phenotypes simultaneously. Herein, a step-wise strategy is developed for fabricating expandable human macromass cartilage (macro-cartilage) in a 3D condition by employing human polydactyly chondrocytes and a screen-defined serum-free customized culture (CC). CC-induced chondrocytes demonstrate improved cell plasticity, expressing chondrogenic biomarkers after a 14.59-times expansion. Crucially, CC-chondrocytes form large-size cartilage tissues with average diameters of 3.25 ± 0.05 mm, exhibiting abundant homogenous matrix and intact structure without a necrotic core. Compared with typical culture, the cell yield in CC increases 2.57 times, and the expression of cartilage marker collagen type II increases 4.70 times. Transcriptomics reveal that this step-wise culture drives a proliferation-to-differentiation process through an intermediate plastic stage, and CC-chondrocytes undergo a chondral lineage-specific differentiation with an activated metabolism. Animal studies show that CC macro-cartilage maintains a hyaline-like cartilage phenotype in vivo and significantly promotes the healing of large cartilage defects. Overall, an efficient expansion of human macro-cartilage with superior regenerative plasticity is achieved, providing a promising strategy for joint regeneration.

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.

Clinical Presentations and Diagnostic Imaging of VACTERL Association

Background: VACTERL association consists of Vertebral, Anorectal, Cardiac, Tracheo-Esophageal, Renal, and Limb defects. The diagnosis depends on the presence of at least three of these structural abnormalities. Methods: The clinical presentation and diagnostic prenatal imaging of VACTERL association are comprehensively reviewed. Results: The most common feature is a vertebral anomaly, found in 60-80% of cases. Tracheo-esophageal fistula is seen in 50-80% of cases and renal malformations in 30% of patients. Limb defects including thumb aplasia/hypoplasia, polydactyly, and radial agenesis/hypoplasia are present in 40-50% of cases. Anorectal defects, like imperforate anus/anal atresia, are challenging to detect prenatally. Conclusion: The diagnosis of VACTERL association mostly relies on imaging techniques such as ultrasound, computed tomography, and magnetic resonance. Differential diagnosis should exclude similar diseases such as CHARGE and Townes-Brocks syndromes and Fanconi anemia. New insights into genetic etiology have led to recommendations of chromosomal breakage investigation for optimal diagnosis and counseling.

Identification of GLI1 and KIAA0825 Variants in Two Families with Postaxial Polydactyly

Polydactyly is a rare autosomal dominant or recessive appendicular patterning defect of the hands and feet, phenotypically characterized by the duplication of digits. Postaxial polydactyly (PAP) is the most common form and includes two main types: PAP type A (PAPA) and PAP type B (PAPB). Type A involves a well-established extra digit articulated with the fifth or sixth metacarpal, while type B presents a rudimentary or poorly developed superfluous digit. Pathogenic variants in several genes have been identified in isolated and syndromic forms of polydactyly. The current study presents two Pakistani families with autosomal recessive PAPA with intra- and inter-familial phenotype variability. Whole-exome sequencing and Sanger analysis revealed a novel missense variant in KIAA0825 (c.3572C>T: p.Pro1191Leu) in family A and a known nonsense variant in GLI1 (c.337C>T: p.Arg113*) in family B. In silico studies of mutant KIAA0825 and GLI1 proteins revealed considerable structural and interactional modifications that suggest an abnormal function of the proteins leading to the disease phenotype. The present study broadens the mutational spectrum of KIAA0825 and demonstrates the second case of a previously identified GLI1 variant with variable phenotypes. These findings facilitate genetic counseling in Pakistani families with a polydactyly-related phenotype.

Update of surgical treatment of polydactyly

PURPOSE OF REVIEW

Polydactyly presents with variable extent of duplication and may involve preaxial/radial (hand)/medial (foot), postaxial/ulnar (hand)/lateral (foot) or central duplication. This review will summarize recent advancements in the surgical management of this common entity.

RECENT FINDINGS

Modifications to classification systems aim to help guide surgical management of polydactyly. Attempts have been made at quantifying preoperative angulation of the duplicated digits to minimize the chance of residual or recurrent deformity after surgical reconstruction. As a result, consideration should be given to the need for soft tissue correction vs. osteotomy to optimize the clinical outcome. On-top plasty is an option that may be beneficial in 'unequal' preaxial polydactyly, where neither duplicate is preferred on its own.

SUMMARY

Polydactyly is one of the most common congenital anomalies in the hands and feet. Determination of surgical intervention often begins with classification systems that exist, which primarily separate these into preaxial, postaxial, and central. Referral for surgical consideration is indicated, given the management is often surgical.

Preaxial polydactyly of the foot in an adult patient diagnosed by X-ray after a trauma

Polydactyly, or hyperdactyly, is a frequent malformation, with a reported incidence between 0.37 and 1.2 per 1000 live births. Most cases encountered in medical practice are sporadic cases, usually presenting one-sided manifestations. More frequently, polydactyly can be detected prenatally through an ultrasound examination, if not, it is usually diagnosed at birth, during the first physical examination. Although the clinical diagnosis is relatively easy in patients with manifest cases, it can sometimes be present with mild or partial forms that are not clinically evident on physical examination, resulting in later diagnosis and treatment. We reported a particular case of polydactyly of the foot not clinically manifest, diagnosed in a 39-year-old Caucasian Male patient with a history of recurrent localized pain in the big toe often associated with subungual bleeding, since he was a child who came to our emergency room following a car accident. Polydactyly is a frequently reported congenital malformation which may present in many different varieties of deformities. In this case, the X-ray, which was required after a car accident, leads to the incidental diagnosis of polydactyly in an adult patient. As described, because of the functional limitations related to this malformation, as well as to limit recurrent pain, and subungual anomalies, the patient underwent to a surgical correction to improve its quality of life.

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.

An unusual manifestation of asymmetric polydactyly of both feet and symmetrical polydactyly of both hands

In the routine treatment at the hospital, it was observed that a 31-year-old Asian woman developed foot pain after work, with clinical manifestations including local tenderness, abrasion, and a rare case of polydactyly with bilateral foot asymmetry. In addition, we also found that the patient had two-handed symmetric polydactyly. According to our observations, there seem to be few similar cases reported in the past of a two-handed symmetric polydactyly combined with a feet asymmetry polydactyly in the same person, so this is a relatively rare reported case of polydactyly. This paper aims to present detailed case report and discuss related diseases in a morphological and clinical study.

Genetic overview of postaxial polydactyly: Updated classification

Polydactyly or polydactylism, also known as a hyperdactyly, is a congenital limb defect with various morphologic phenotypes. Apart from physical and functional impairments, the presence of polydactyly is an indication of an underlying syndrome in the newborn. Usually, it follows as an autosomal dominant/recessive inheritance pattern with defects in the limb development's anteroposterior patterning. Although mutations in several genes have been associated with polydactyly; however, the exact underlying cause, pathways, and disease mechanisms are still unexplored, thus making it of multi-factorial origin. Polydactyly is divided into three subtypes; radial, ulnar, and central polydactyly. So far, 11 loci (PAPA1-PAPA11) and seven human genes have been reported to cause non-syndromic postaxial polydactyly in humans, including the ZNF141, GLI3, IQCE, GLI1, FAM92A1, KIAA0825, and DACH1. In this review, we discuss emerging evidences of clinical and molecular characterization of polydactyly types in term of the involvement of newly associated genes and loci for non-syndromic postaxial polydactyly, and how these might impact our understanding of the genetic mechanisms and molecular etiology involved in the cause of polydactyly.

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.

Burden of congenital and hereditary anomalies in the war-affected territory at Pakistan-Afghanistan border

Background

Pashtun populations of Pakistan are the victim of long-lasting military combats, rendering 1.9 million inhabitants internally displaced. Studies highlighting congenital and hereditary anomalies in these populations are deficient.

Objectives

To elucidate the spectrum anomalies in the north-western war-affected territories of Pakistan.

Methods

A cross-sectional study was carried out from 2017 to 2019 and individuals or families with anomalies were ascertained through convenience and cluster random sampling. Phenotypic and pedigree data and information on bio-demographic variables were collected. Descriptive statistics were applied.

Results

A total of 361 independent individuals or families with anomalies were recruited. The anomalies were grouped into 8 major and 72 minor entities. Among major categories, neurological disorders had the highest representation (n = 100; proportion: 0.277; 95% CI: 0.231-0.323), followed by sensorineural defects (n = 70; prop.: 0.194), limb defects (n = 60; prop.: 0.166), visual impairments (n = 55; prop.: 0.152), and musculoskeletal defects (n = 37; prop.: 0.102). Among the neurological disorders, intellectual disability had the highest occurrence (58%), whereas talipes and limb amputations were the most prominent in limb defects (22% and 20%, respectively). The anomalies had sporadic and isolated presentations most often (76% each), while parental consanguinity was observed in 34% of index cases.

Conclusions

The high incidence of neurological, sensorineural, and limb defects, the preponderance of sporadic cases, and low level of parental consanguinity may indicate a potentially high contribution of nongenetic factors in the etiology of anomalies. The majority of anomalies are the cause of severe disability.

Gattaca as a lens on contemporary genetics: marking 25 years into the film's "not-too-distant" future

The 1997 film Gattaca has emerged as a canonical pop culture reference used to discuss modern controversies in genetics and bioethics. It appeared in theaters a few years prior to the announcement of the "completion" of the human genome (2000), as the science of human genetics was developing a renewed sense of its social implications. The story is set in a near-future world in which parents can, with technological assistance, influence the genetic composition of their offspring on the basis of predicted life outcomes. The current moment-25 years after the film's release-offers an opportunity to reflect on where society currently stands with respect to the ideas explored in Gattaca. Here, we review and discuss several active areas of genetic research-genetic prediction, embryo selection, forensic genetics, and others-that interface directly with scenes and concepts in the film. On its silver anniversary, we argue that Gattaca remains an important reflection of society's expectations and fears with respect to the ways that genetic science has manifested in the real world. In accompanying supplemental material, we offer some thought questions to guide group discussions inside and outside of the classroom.

Pallister-Hall syndrome, GLI3, and kidney malformation

Pallister-Hall syndrome (PHS) is a rare autosomal dominant disease diagnosed by the presence of hypothalamic hamartoma, mesoaxial polydactyly and a truncating variant in the middle third of the GLI-Kruppel family member 3 (GLI3) gene. PHS may also include a wide range of clinical phenotypes affecting multiple organ systems including congenital anomalies of the kidney and urinary tract (CAKUT). The observed clinical phenotypes are consistent with the essential role of GLI3, a transcriptional effector in the hedgehog (Hh) signaling pathway, in organogenesis. However, the mechanisms by which truncation of GLI3 in PHS results in such a variety of clinical phenotypes with variable severity, even within the same organ, remain unclear. In this study we focus on presentation of CAKUT in PHS. A systematic analysis of reported PHS patients (n = 78) revealed a prevalence of 26.9% (21/78) of CAKUT. Hypoplasia (± dysplasia) and agenesis were the two main types of CAKUT; bilateral and unilateral CAKUT were reported with equal frequency. Examination of clinical phenotypes with CAKUT revealed a significant association between CAKUT and craniofacial defects, bifid epiglottis and a Disorder of Sex Development, specifically affecting external genitalia. Lastly, we determined that PHS patients with CAKUT predominately had substitution type variants (as opposed to deletion type variants in non-CAKUT PHS patients) in the middle third of the GLI3 gene. These results provide a foundation for future work aimed at uncovering the molecular mechanisms by which variant GLI3 result in the wide range and severity of clinical features observed in PHS.

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.

First record of polydactyly for a European bat, Myotis daubentonii (Chiroptera, Vespertilionidae)

Despite being one of the most common congenital hand abnormalities in humans, polydactyly remains extremely rare in bats. To date, it has been observed only in two insectivorous families in North America (Molossidae and Vespertilionidae) and a single case for the New World fruit bats (Phyllostomidae). We report the first case of polydactyly in a European bat – a Myotis daubentonii (Vespertilionidae), with eight toes. The bat was found alive, hibernating in the Natura 2000 site (PLH080003 “Nietoperek”) in Poland.

A novel variant of GLI3, p.Asp1514Thrfs*5, is identified in a Chinese family affected by polydactyly

Background

Polydactyly is a common congenital malformation characterized by the presence of supernumerary fingers or toes. In this case study, we sought to identify the causative pathogenic factor in a family from a northern region of China affected by non‐syndromic postaxial polydactyly (PAP).

Methods

After recruiting a three‐generation family with PAP, whole‐exome sequencing was performed to identify the causative variant. In silico analysis and Sanger sequencing were used to validate the variant.

Results

We identified a novel heterozygous frameshift variant (NM_000168.6:c.4540delG, p.Asp1514Thrfs*5) in the transcriptional activator (TA1) domain of the GLI3 gene.

Conclusion

The novel frameshift variant identified in this study further confirms the relationship between non‐syndromic PAP and GLI3 and extends the previously established mutational and phenotypic spectra of GLI3.

Examination of Postoperative Outcomes Using Morphological and X-Ray Classifications and Selection of the Toe to Be Excised in Postaxial Polydactyly of the Foot

The treatment of postaxial polydactyly requires excision of the medial fifth or lateral sixth toe, and separation of the adjacent fourth/fifth toes if the adjacent toes exhibit skin syndactyly. Morphological changes in the retained toes and reoperation are common problems after such surgery. This study examined the effects of preoperative classifications and selecting the medial fifth or lateral sixth toe for excision on the postoperative outcomes of surgery for postaxial polydactyly. From April 2006 to March 2019, surgery for postaxial polydactyly was performed on 55 feet in 49 patients. The patients' mean age at surgery was 28.8 months. Postoperative esthetic and bone alignment scores, the reoperation rate, and postoperative dysfunction were examined. The postoperative esthetic and bone alignment evaluations were performed by examining postoperative photograph and X-ray images using original scoring systems. The surgical procedure was chosen by the surgeon-in-charge during a preoperative conference after considering the toe growth and bone alignment. In the postoperative esthetic evaluation, excising the lateral sixth toe produced significantly better outcomes than excising the medial fifth toe. The morphological classification also indicated that excising the lateral sixth toe produced better outcomes, as it resulted in the bifurcated toes being clearly independent. Interestingly, the postoperative X-ray-based bone alignment score was not correlated with the esthetic score. The reoperation rate tended to be high after medial fifth toe excision. There were no postoperative functional complications. Lateral sixth toe excision for postaxial polydactyly of the foot produces good postoperative esthetic outcomes.

Pediatric Forefoot Deformities

This article explores different pediatric forefoot deformities including syndactyly, polydactyly, macrodactyly, curly toe, and congenital hallux varus. The epidemiology and genetic background are reviewed for each condition. Preferred treatment options and recommended surgical techniques are discussed with review of the current literature.

ZPA Regulatory Sequence Variants in Chinese Patients With Preaxial Polydactyly: Genetic and Clinical Characteristics

Preaxial polydactyly (PPD) is a common congenital abnormality with an incidence of 0.8-1.4% in Asians, characterized by the presence of extra digit(s) on the preaxial side of the hand or foot. PPD is genetically classified into four subtypes, PPD type I-IV. Variants in six genes/loci [including GLI family zinc finger 3 (GLI3), ZPA regulatory sequence (ZRS), and pre-ZRS region] have been identified in PPD cases. Among these loci, ZRS is, perhaps, the most special and well known, but most articles only reported one or a few cases. There is a lack of reports on the ZRS-variant frequency in patients with PPD. In this study, we recruited 167 sporadic or familial cases (including 154 sporadic patients and 13 families) with PPD from Central-South China and identified four ZRS variants in four patients (2.40%, 4/167), including two novel variants (ZRS131A > T/chr7:g.156584439A > T and ZRS474C > G/chr7:g.156584096C > G) and two known variants (ZRS428T > A/chr7:g.156584142T > A and ZRS619C > T/chr7:g.156583951C > T). ZRS131A > T and ZRS428T > A were detected in PPD I cases and ZRS474C > G and ZRS619C > T combinedly acted to cause PPD II. The detectable rate of ZRS variants in PPD I was 1.60% (2/125), while PPD II was significantly higher (9.52%, 2/21). Three bilateral PPD cases harbored ZRS variants (13.64%, 3/22), suggesting that bilateral PPD was more possibly caused by genetic etiologies. This study identified two novel ZRS variants, further confirmed the association between ZRS and PPD I and reported a rare PPD II case resulted from the compound heterozygote of ZRS. This investigation preliminarily evaluated a ZRS variants rate in patients with PPD and described the general picture of PPD in Central-South China.

Growth in Joubert syndrome: Growth curves and physical measurements with correlation to genotype and hepatorenal disease in 170 individuals

Joubert syndrome (JS) is a genetically heterogenous disorder of nonmotile cilia with a characteristic "molar tooth sign" on axial brain imaging. Clinical features can include developmental delay, kidney failure, liver disease, and retinal dystrophy. Prospective growth and measurement data on 170 individuals with JS were collected, including parental measurements, birth measurements, and serial measures when available. Analysis of growth parameters in the context of hepatorenal disease, genotype, and other features was performed on 100 individuals assessed at the National Institutes of Health Clinical Center. Individuals with JS had shorter stature despite normal growth velocity and were shorter than predicted for mid-parental height. Individuals were lighter in weight, resulting in a normal body mass index (BMI). Head circumference was larger, averaging 1.9 Z-scores above height. At birth, head circumference was proportional to length. Individuals with variants in CPLANE1 had a larger head circumference compared to other genotypes; individuals with evidence of liver disease had lower weight and BMI; and individuals with polydactyly had shorter height. Here we present growth curves and physical measurements for Joubert syndrome based on the largest collection of individuals with this disorder to aid in clinical management and diagnosis.

Molecular Bases of Human Malformation Syndromes Involving the SHH Pathway: GLIA/R Balance and Cardinal Phenotypes

Human hereditary malformation syndromes are caused by mutations in the genes of the signal transduction molecules involved in fetal development. Among them, the Sonic hedgehog (SHH) signaling pathway is the most important, and many syndromes result from its disruption. In this review, we summarize the molecular mechanisms and role in embryonic morphogenesis of the SHH pathway, then classify the phenotype of each malformation syndrome associated with mutations of major molecules in the pathway. The output of the SHH pathway is shown as GLI activity, which is generated by SHH in a concentration-dependent manner, i.e., the sum of activating form of GLI (GLIA) and repressive form of GLI (GLIR). Which gene is mutated and whether the mutation is loss-of-function or gain-of-function determine in which concentration range of SHH the imbalance occurs. In human malformation syndromes, too much or too little GLI activity produces symmetric phenotypes affecting brain size, craniofacial (midface) dysmorphism, and orientation of polydactyly with respect to the axis of the limb. The symptoms of each syndrome can be explained by the GLIA/R balance model.

Rare phenotype: Hand preaxial polydactyly associated with LRP6-related tooth agenesis in humans

Low-density lipoprotein receptor-related protein 6 (LRP6) is a pathogenic gene of selective tooth agenesis-7 (OMIM#616724). Although the malformation of the digits and fore- and hindlimbs has been reported in Lrp6-deficient mice, it has been rarely discovered in humans with LRP6 mutations. Here, we demonstrate an unreported autosomal dominant LRP6 heterozygous mutation (c.2840 T > C;p.Met947Thr) in a tooth agenesis family with hand polydactyly, and another unreported autosomal dominant LRP6 heterozygous mutation (c.1154 G > C;p.Arg385Pro) in a non-syndromic tooth agenesis family. Bioinformatic prediction demonstrated the deleterious effects of the mutations, and LRP6 structure changes suggested the corresponding functional impairments. Analysis on the pattern of LRP6-related tooth agenesis demonstrated the maxillary lateral incisor was the most affected. Our study report that LRP6 mutation might be associated with hand preaxial polydactyly in humans, which broaden the phenotypic spectrum of LRP6-related disorders, and provide valuable information on the characteristics of LRP6-related tooth agenesis.

Polymetatarsia of the Foot without Polydactyly: A Case Report

CASE

We report a rare case of polymetatarsia without polydactyly. Our patient presented with pain and difficulty with shoewear. Radiographs showed an accessory metatarsal arising from the lateral aspect of the fourth metatarsal proximal metaphysis, fusing distally with the medial aspect of the fifth metatarsal head to form a single metatarsophalangeal joint. He was treated with a chevron osteotomy of the conjoined complex and an Akins osteotomy of the fifth proximal phalanx. Our patient recovered functionally, and his pain improved postoperatively.

CONCLUSION

The chevron osteotomy is an option for treating polymetatarsia without polydactyly with the aim of reducing the forefoot width.

LEVEL OF EVIDENCE

Case study, level 5.

Prenatal diagnosis of triphalangeal thumb-polysyndactyly syndrome by ultrasonography combined with genetic testing: A case report

BACKGROUND

Triphalangeal thumb-polysyndactyly syndrome (TPT-PS) is a rare type of congenital limb deformity, and most studies focus on the genetics. Case reports of the sonographic characteristics of TPT-PS during pregnancy are rare.

CASE SUMMARY

A 30-year-old woman (G3P1) who had pregnancies with TPT-PS fetuses is presented. The possibility of TPT-PS was shown by ultrasound performed at the 19^th wk of pregnancy, featuring hands with six metacarpals, an extra digit at the 5^th finger side, and an abnormally widened thumb. Whole-exome sequencing was subsequently conducted. The results showed that exons 1-17 of the LMBR1 gene had a heterozygous duplication, with a length of approximately 253 kb.

CONCLUSION

We suggest prenatal ultrasound examination combined with genetic testing to diagnose TPT-PS accurately and to help clinicians and patients make decisions.

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.

Congenital limb defects in a married female population of the Rahim Yar Khan District in Pakistan

Background

Congenital limb defects (CLD) have a range of phenotypes and can be a substantial cause of disability. The prevalence of CLD in the adult population of Pakistan is not well described.

Objectives

To investigate the prevalence of CLD and their associated factors in a married female population of the Rahim Yar Khan (RYK) District in Pakistan.

Methods

A cross-sectional population-based study was conducted in 4 tehsils of RYK District, and married women and girls from 22 different localities were enrolled by convenience sampling in public places and through door-to-door visits. Data regarding limb phenotype and demographic variables were obtained from participants.

Results

We enrolled 2,204 married women and girls. We found 11 participants with CLD suggesting a prevalence of 4.99/1,000 (proportion: 0.005; 95% confidence interval [CI] <0.001-0.01). Polydactyly was the most frequent (n = 5; prevalence: 2.27/1,000), followed by others in the following sequence: brachydactyly (n = 4; prevalence: 1.81/1,000), camptodactyly (n = 1; prevalence: 0.45/1,000), and oligodactyly (n = 1; prevalence: 0.45/1,000). The odds of occurrence of CLD were higher in individuals originating from Khanpur tehsil (odds ratio [OR] 2.05; 95% CI 0.37-11.27), speaking languages other than Punjabi and Saraiki (OR 2.35; 95% CI 0.24-22.80), belonging to Araien caste (OR 2.35; 95% CI: 0.24-22.80), of a nuclear family (OR 3.35; 95% CI 0.79-16.97), or having parental consanguinity (OR 1.87; 95% CI 0.49-7.06).

Conclusion

Preliminary estimate of CLD prevalence in the married female sample population in RYK appears high compared with estimates from birth defects registries in other countries.

Polydactyly of the Foot: A Review

Pediatric foot polydactyly presents in a wide variety of deformities from single extra digits attached only by a narrow soft-tissue connection to complex central foot duplications with tarsal bone duplication. The goal of surgical reconstruction is a stable, mobile, pain-free foot with five cosmetically appealing toes that allows for normal footwear and painless ambulation. This review covers the incidence, genetics and embryology, classification, presentation and natural history, physical examination, radiographic assessment, and surgical intervention for all types of foot polydactyly.

Maternal exposure to ambient SO2 and risk of polydactyly and syndactyly: a population-based case-control study in Liaoning Province, China

Evidence links exposure to maternal sulfur dioxide (SO₂) and the risk of limb defects have been inconsistent. To investigate associations between SO₂ exposure during preconception and the first trimester and risks of polydactyly and syndactyly. The study population was acquired from the Maternal and Child Health Certificate Registry of Liaoning Province between 2010 to 2015, and consisted of 2605 polydactyly, 595 syndactyly cases, and 7950 controls. Ambient air pollutants levels were retrieved from air quality monitoring stations. We used multivariable logistic regression model to assess the adjusted odds ratios (ORs) and 95% confidence intervals (CIs). We found that exposure to increased SO₂ concentrations was associated with polydactyly during both the 3 months preconception (OR_{Q4 vs. Q1} = 3.76; 95% CI 2.61, 5.42; per 10 μg/m³ increment: OR = 1.07; 95% CI 1.04, 1.10) and the first trimester (OR_{Q4 vs. Q1} = 2.03; 95% CI 1.41, 2.92; per 10 μg/m³ increment: OR = 1.07; 95% CI 1.03, 1.11). However, we only observed increased risk for syndactyly in the analysis of high vs. low quartiles (three months preconception: OR_{Q4 vs. Q1} = 3.72; 95% CI 2.05, 6.75; first trimester: OR_{Q4 vs. Q1} = 1.98; 95% CI 1.11, 3.51). Most results of analyses based on single-month exposure window generally showed similar positive associations. Additionally, these findings were broadly consistent across subgroups and sensitivity analyses. Maternal SO₂ exposure increase the risk of polydactyly and syndactyly.

Maternal occupational exposure to chemicals in the textile factory during pregnancy is associated with a higher risk of polydactyly in the offspring

Background: The number of children with polydactyly seen in our clinic is increasing. In addition to genetic factors, an influence of environmental effects during pregnancy is becoming increasingly apparent; however, epidemiological data on these effects are lacking.Methods: This hospital-based, case-control study enrolled 143 patients with polydactyly and 286 control patients with no genetic diseases, to evaluate the association between maternal exposure to a textile factory environment during pregnancy and the likelihood of giving birth to a child with polydactyly.Results: Maternal exposure to a textile factory environment during pregnancy was associated with an increased risk of giving birth to a child with polydactyly (exposure to textile factory environment: unadjusted odds ratio (OR) = 3.31, 95% confidence interval (CI) = 1.75-6.27, p = .0002; work seniority of exposed occupation: unadjusted OR 1.28, 95% CI = 1.13-1.47, p = .0002). Covariate screening indicated that certain risk factors (family monthly income per capita, mother's emotional state during pregnancy, colporrhagia, passive smoking, smoking, and history of consanguineous marriage) were potential confounding factors. After adjusting for these variables, the OR of exposure to a textile factory environment remained significant (exposure to textile factory environment: adjusted OR = 3.08, 95% CI = 1.32-7.19, p = .0094; work seniority of exposed occupation: adjusted OR = 1.58, 95% CI = 1.20-2.08, p = .0010). The risk of polydactyly increased with the number of years of employment.Conclusions: Maternal exposure to a textile factory environment appears to be a risk factor for polydactyly in newborns.

Genetic heterogeneity of polydactyly in Maine Coon cats

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.

Novel mutations of TCTN3/LTBP2 with cellular function changes in congenital heart disease associated with polydactyly

Congenital heart disease (CHD) associated with polydactyly involves various genes. We aimed to identify variations from genes related to complex CHD with polydactyly and to investigate the cellular functions related to the mutations. Blood was collected from a complex CHD case with polydactyly, and whole exome sequencing (WES) was performed. The CRISPR/Cas9 system was used to generate human pluripotent stem cell with mutations (hPSCs-Mut) that were differentiated into cardiomyocytes (hPSC-CMs-Mut) and analysed by transcriptomics on day 0, 9 and 13. Two heterozygous mutations, LTBP2 (c.2206G>A, p.Asp736Asn, RefSeq NM_000428.2) and TCTN3 (c.1268G>A, p.Gly423Glu, RefSeq NM_015631.5), were identified via WES but no TBX5 mutations were found. The stable cell lines of hPSCs-LTBP2^mu /TCTN3^mu were constructed and differentiated into hPSC-CMs-LTBP2^mu /TCTN3^mu . Compared to the wild type, LTBP2 mutation delayed the development of CMs. The TCTN3 mutation consistently presented lower rate and weaker force of the contraction of CMs. For gene expression pattern of persistent up-regulation, pathways in cardiac development and congenital heart disease were enriched in hPSCs-CM-LTBP2^mu , compared with hPSCs-CM-WT. Thus, the heterozygous mutations in TCTN3 and LTBP2 affect contractility (rate and force) of cardiac myocytes and may affect the development of the heart. These findings provide new insights into the pathogenesis of complex CHD with polydactyly.

Extreme bilateral polydactyly in a wild-caught western grey kangaroo

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.

Association between maternal exposure to PM10 and polydactyly and syndactyly: A population-based case-control study in Liaoning province, China

BACKGROUND

The number of studies on air pollution with birth defects as the primary outcome has increased dramatically over the past two decades, but the potential role of specific air pollutants in congenital limb anomalies remains unclear.

OBJECTIVES

To evaluate associations between preconception and first-trimester PM₁₀ exposure and polydactyly and syndactyly in a population-based case-control study.

METHODS

Polydactyly cases (n = 2605), syndactyly cases (n = 595), and controls without any birth defects (n = 7950) born between 2010 and 2015 were selected from the Maternal and Child Health Certificate Registry of Liaoning Province. The monthly mean PM₁₀ concentrations were obtained from 75 air monitoring stations, and the exposure assessment was based on the mean concentration of all stations in mother's residential city. A multivariable logistic regression model was constructed to calculate adjusted odds ratios (aORs) and 95% confidence intervals (CIs).

RESULTS

PM₁₀ exposure was positively associated with the risks of polydactyly (preconception: aOR_{T3 vs. T1} = 1.95, 95% CI 1.56-2.45, aOR = 1.06, 95% CI 1.01-1.10 [per 10-μg/m³ increment]; first-trimester: aOR_{T3 vs. T1} = 2.51, 95% CI 2.00-3.15) and syndactyly (preconception: aOR_{T3 vs. T1} = 2.86, 95% CI 1.98-4.13, aOR = 1.11, 95% CI 1.03-1.20 [per 10-μg/m³ increment]; first-trimester: aOR_{T3 vs. T1} = 3.10, 95% CI 2.11-4.56). Analyses based on single month exposure windows basically showed similar positive associations. Additionally, these findings were robust in sensitivity analyses and broadly consistent across subgroups.

CONCLUSION

Our study suggest that preconception and first-trimester PM₁₀ exposures are related to increased risks of polydactyly and syndactyly.

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.

RAB23 coordinates early osteogenesis by repressing FGF10-pERK1/2 and GLI1

Mutations in the gene encoding Ras-associated binding protein 23 (RAB23) cause Carpenter Syndrome, which is characterized by multiple developmental abnormalities including polysyndactyly and defects in skull morphogenesis. To understand how RAB23 regulates skull development, we generated Rab23-deficient mice that survive to an age where skeletal development can be studied. Along with polysyndactyly, these mice exhibit premature fusion of multiple sutures resultant from aberrant osteoprogenitor proliferation and elevated osteogenesis in the suture. FGF10-driven FGFR1 signaling is elevated in Rab23^-/-sutures with a consequent imbalance in MAPK, Hedgehog signaling and RUNX2 expression. Inhibition of elevated pERK1/2 signaling results in the normalization of osteoprogenitor proliferation with a concomitant reduction of osteogenic gene expression, and prevention of craniosynostosis. Our results suggest a novel role for RAB23 as an upstream negative regulator of both FGFR and canonical Hh-GLI1 signaling, and additionally in the non-canonical regulation of GLI1 through pERK1/2.

Novel heterozygous sequence variant in the GLI1 underlies postaxial polydactyly

Polydactyly is one of the most common congenital abnormal phenotype of autopod, which is characterized by extra supernumerary digit in hands/feet with or without well-developed bony structure within the digits. Preaxial polydactyly (PPD), postaxial polydactyly (PAP), and meso-axial (central) polydactyly are three different isoforms of polydactyly. Genetically, at least 10 genes have been identified causing nonsyndromic polydactyly. In the present study, we have investigated a large family segregating autosomal dominant form of nonsyndromic polydactyly. Whole exome sequencing followed by Sanger sequencing revealed a novel heterozygous missense variant (NM_005269.3; c.1064C>A; p.(Thr355Asn) in the gene GLI1 segregating with the disease phenotype within the family. This study presents first familial case of autosomal dominant form of polydactyly caused by the GLI1 variant.

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.

Whole genome resequencing reveals an association of ABCC4 variants with preaxial polydactyly in pigs

Background

Polydactyly is one of the most common congenital limb dysplasia in many animal species. Although preaxial polydactyly (PPD) has been comprehensively studied in humans as a common abnormality, the genetic variations in other animal species have not been fully understood. Herein, we focused on the pig, as an even-toed ungulate mammal model with its unique advantages in medical and genetic researches, two PPD families consisting of four affected and 20 normal individuals were sequenced.

Results

Our results showed that the PPD in the sampled pigs were not related to previously reported variants. A strong association was identified at ABCC4 and it encodes a transmembrane protein involved in ciliogenesis. We found that the affected and normal individuals were highly differentiated at ABCC4, and all the PPD individuals shared long haplotype stretches as compared with the unaffected individuals. A highly differentiated missense mutation (I85T) in ABCC4 was observed at a residue from a transmembrane domain highly conserved among a variety of organisms.

Conclusions

This study reports ABCC4 as a new candidate gene and identifies a missense mutation for PPD in pigs. Our results illustrate a putative role of ciliogenesis process in PPD, coinciding with an earlier observation of ciliogenesis abnormality resulting in pseudo-thumb development in pandas. These results expand our knowledge on the genetic variations underlying PPD in animals.

A Review of Benign Congenital Anomalies

Benign congenital anomalies are common in neonates. Some of these common benign congenital anomalies include preauricular pits, sacral dimples, supernumerary digits, accessory nipple, and natal teeth. It is important for health care providers who take care of newborns to recognize these benign anomalies so that unnecessary evaluations and investigations are not performed. However, some of these anomalies may be associated with clinically significant conditions. In this article, we discuss when further evaluation should be performed in babies presenting with these common benign congenital anomalies. [Pediatr Ann. 2020;49(2):e66-e70.].

Novel IQCE variations confirm its role in postaxial polydactyly and cause ciliary defect phenotype in zebrafish

Polydactyly is one of the most frequent inherited defects of the limbs characterized by supernumerary digits and high-genetic heterogeneity. Among the many genes involved, either in isolated or syndromic forms, eight have been implicated in postaxial polydactyly (PAP). Among those, IQCE has been recently identified in a single consanguineous family. Using whole-exome sequencing in patients with uncharacterized ciliopathies, including PAP, we identified three families with biallelic pathogenic variations in IQCE. Interestingly, the c.895_904del (p.Val301Serfs*8) was found in all families without sharing a common haplotype, suggesting a recurrent mechanism. Moreover, in two families, the systemic phenotype could be explained by additional pathogenic variants in known genes (TULP1, ATP6V1B1). RNA expression analysis on patients' fibroblasts confirms that the dysfunction of IQCE leads to the dysregulation of genes associated with the hedgehog-signaling pathway, and zebrafish experiments demonstrate a full spectrum of phenotypes linked to defective cilia: Body curvature, kidney cysts, left-right asymmetry, misdirected cilia in the pronephric duct, and retinal defects. In conclusion, we identified three additional families confirming IQCE as a nonsyndromic PAP gene. Our data emphasize the importance of taking into account the complete set of variations of each individual, as each clinical presentation could finally be explained by multiple genes.