Preaxial Polydactyly Type Research Articles

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.

Variant type and position predict two distinct limb phenotypes in patients with GLI3-mediated polydactyly syndromes

IntroductionPathogenic DNA variants in the GLI-Kruppel family member 3 (GLI3) gene are known to cause multiple syndromes: for example, Greig syndrome, preaxial polydactyly-type 4 (PPD4) and Pallister-Hall syndrome. Out of...

A GLI3 variant leading to polydactyly in heterozygotes and Pallister-Hall-like syndrome in a homozygote.

Variants in transcriptional activator Gli Kruppel Family Member 3 (GLI3) have been reported to be associated with several phenotypes including Greig cephalopolysyndactyly syndrome (MIM #175700), Pallister-Hall syndrome (PHS) (MIM #146510), postaxial polydactyly types A1 (PAPA1) and B (PAPB) (MIM #174200), and preaxial polydactyly type 4 (MIM #174700). All these disorders follow an autosomal dominant pattern of inheritance. Hypothalamic hamartomas (MIM 241800) is associated with somatic variants in GLI3. We report a related couple with parents having PAPA1 and PAPB, who had a fetus with a phenotype most compatible with PHS. Molecular analyses demonstrated homozygosity for a pathogenic GLI3 variant (c.1927C > T; p. Arg643*) in the fetus and heterozygosity in the parents. The genetic analysis in this family demonstrates that heterozygosity and homozygosity for the same GLI3 variant can cause a different phenotype. Furthermore, the occurrence of Pallister-Hall-like syndrome in a homozygous patient should be taken into account in genetic counseling of families with PAPA1/PAPB.

A novel ZRS variant causes preaxial polydactyly type I by increased sonic hedgehog expression in the developing limb bud

PurposePreaxial polydactyly (PPD) is a common congenital hand malformation classified into four subtypes (PPD I–IV). Variants in the zone of polarizing activity regulatory sequence (ZRS) within intron 5 of the LMBR1 gene are linked to most PPD types. However, the genes responsible for PPD I and the underlying mechanisms are unknown. MethodsA rare large four-generation family with isolated PPD I was subjected to genome-wide genotyping and sequence analysis. In vitro and in vivo functional studies were performed in Caco-2 cells, 293T cells, and a knockin transgenic mouse model. ResultsA novel g.101779T>A (reference sequence: NG_009240.2; position 446 of the ZRS) variant segregates with all PPD I–affected individuals. The knockin mouse with this ZRS variant exhibited PPD I phenotype accompanying ectopic and excess expression of Shh. We confirmed that HnRNP K can bind the ZRS and SHH promoters. The ZRS mutant enhanced the binding affinity for HnRNP K and upregulated SHH expression. ConclusionOur results identify the first PPD I disease-causing variant. The variant leading to PPD I may be associated with enhancing SHH expression mediated by HnRNP K. This study adds to the ZRS-associated syndromes classification system for PPD and clarifies the underlying molecular mechanisms.

Novel GLI3 variant causes Greig cephalopolysyndactyly syndrome in three generations of a Lithuanian family.

BackgroundPreaxial polydactyly type IV, also referred as polysyndactyly, has been described in a few syndromes. We present three generations of a family with preaxial polydactyly type IV and other clinical features of Greig cephalopolysyndactyly syndrome (GCPS).Methods and resultsSequencing analysis of the GLI3 coding region identified a novel donor splice site variant NC_000007.14(NM_000168.6):c.473+3A>T in the proband and the same pathogenic variant was subsequently identified in other affected family members. Functional analysis based on Sanger sequencing of the proband's complementary DNA (cDNA) sample revealed that the splice site variant c.473+3A>T disrupts the original donor splice site, thus leading to exon 4 skipping. Based on further in silico analysis, this pathogenic splice site variant consequently results in a truncated protein NP_000159.3:p.(His123Argfs*57), which lacks almost all functionally important domains. Therefore, functional cDNA analysis confirmed that the haploinsufficiency of the GLI3 is the cause of GCPS in the affected family members.ConclusionDespite the evidence provided, pathogenic variants in the GLI3 do not always definitely correlate with syndromic or nonsyndromic clinical phenotypes associated with this gene. For this reason, further transcriptomic and proteomic evaluation could be suggested.

Whole-exome sequencing revealed a nonsense mutation in STKLD1 causing non-syndromic pre-axial polydactyly type A affecting only upper limb.

Pre-axial polydactyly (PPD) is characterized by well-developed non-functional 1st digit (thumb) duplication in hands and/or feet. It is mostly inherited in autosomal dominant manner. In the present study, two families of Pakistani origin, demonstrating unilateral PPD type A, have been characterized at clinical and genetic levels. Whole-exome sequencing (WES) revealed a nonsense mutation (c.84C > A, p.Tyr28*) in the STKLD1, located on chromosome 9q34.2, in affected individuals of both the families. Our findings report the first direct involvement of the STKLD1 in the digit development and highlight the importance of inclusion of this gene for screening individuals presenting non-syndromic recessive PPD.

A novel missense variant in the GLI3 zinc finger domain in a family with digital anomalies.

Mutations in GLI3, which encodes a transcription factor of the Hedgehog signaling pathway, cause several developmental anomalies linked to inappropriate tissue patterning. Here, we report a novel missense variant in the fifth zinc finger domain of GLI3 (c.1826G>A; p.(Cys609Tyr)) initially identified in a proband with preaxial polydactyly type IV, developmental delay, sensorineural hearing loss, skeletal, and genitourinary anomalies. Additional family members exhibited various digital anomalies such as preaxial polydactyly, syndactyly, and postaxial polydactyly either in isolation or combined. Functional studies of Cys609Tyr GLI3 in cultured cells showed abnormal GLI3 processing leading to decreased GLI3 repressor production, increased basal transcriptional activity, and submaximal GLI reporter activity with Hedgehog pathway activation, thus demonstrating an intriguing molecular mechanism for this GLI3-related phenotype. Given the complexity of GLI3 post-translational processing and opposing biological functions as a transcriptional activator and repressor, our findings highlight the importance of performing functional studies of presumed GLI3 variants. This family also demonstrates how GLI3 variants are variably expressed.

GLI3-related polydactyly: a review.

GLI3 mutations are known to be associated with nine syndromes/conditions in which polydactyly is a feature. In this review, the embryology, pathogenesis, and animal models of GLI3-related polydactyly are discussed first. This is followed by a detailed review of the genotype-phenotype correlations. Based on our review of the literature and our clinical experiences, we recommend viewing GLI3-related syndromes/conditions as four separate entities; each characterized by a specific pattern of polydactyly. These four entities are: the preaxial polydactyly type IV-Greig-acrocallosal spectrum, postaxial polydactyly types A/B, Pallister-Hall syndrome (PHS), and oral-facial-digital overlap syndrome. We also provide illustrative clinical examples from our practice including a family with a novel GLI3 mutation causing PHS. The review also introduces the term 'Forme Fruste' preaxial polydactyly and gives several conclusions/recommendations including the recommendation to revise the current criteria for the clinical diagnosis of PHS.

Clinical study of 459 polydactyly cases in China, 2010 to 2014.

Polydactyly is one of the most common hereditary limb malformations, involving additional digits on the hands and/or feet, which is a very attractive model to appreciate clinical and genetic heterogeneity. A high level of heterogeneity in polydactyly has been identified in different regions. However, such data of the medical literatures for Asian populations are relatively limited. This study was intended to shed light on the phenotypic manifestations of polydactyly in the recruited Chinese population and to characterize the medical literature on this condition. A total of 459 well-characterized polydactyly cases from Shanghai Children's Medical Center were recruited. Their phenotypes, inheritance patterns, and clinical heterogeneity were obtained from clinical medical records. It was found that 4.8% of cases were familial and 95.2% were sporadic. The proportions of preaxial and postaxial polydactyly types were 74.7% and 25.3%, respectively. In preaxial polydactyly, type I formed the overwhelming majority (95.9%). Among the postaxial polydactyly cases, type A was most prevalent at 69.8% and type B was witnessed in 30.2% of cases. Familial and sporadic polydactyly patients mainly had unilateral presentations. A total of 583 limbs with additional digits were recorded in the 459 subjects. Upper limb involvement was more common than lower, and right hand involvement was more common than left for preaxial polydactyly, and lower limb involvement was more common than upper in postaxial polydactyly. This cohort added useful clinical/epidemiological information to the polydactyly literature in the Chinese population and highlighted its marked clinical heterogeneity.

Exome sequencing reveals a novel nonsense mutation of GLI3 in a Chinese family with 'non-syndromic' pre-axial polydactyly.

Polydactyly is a clinically and genetically heterogeneous disorder. In the current report, we present a five-generation Chinese family with non-syndromic pre-axial polydactyly with thumb polydactyly (pre-axial polydactyly type I (PPD-I)) as a major clinical feature. Using whole-exome sequencing (WES), a novel nonsense mutation c.714T>A (p.Y238*) of the glioma-associated oncogene family zinc-finger 3 gene (GLI3) was identified as the pathogenic mutation for this family. Our study has, for the first time, suggested the possible contribution of GLI3 in the patheogenesis of PPD-I, and demonstrated that WES provided an applicable diagnostic tool for identifying mutations in disorders with highly genetical heterogeneity such as polydactyly.

A novel ZRS mutation leads to preaxial polydactyly type 2 in a heterozygous form and Werner mesomelic syndrome in a homozygous form.

Point mutations in the zone of polarizing activity regulatory sequence (ZRS) are known to cause human limb malformations. Although most mutations cause preaxial polydactyly (PPD), triphalangeal thumb (TPT) or both, a mutation in position 404 of the ZRS causes more severe Werner mesomelic syndrome (WMS) for which malformations include the distal arm or leg bones in addition to the hands and/or feet. Of more than 15 reported families with ZRS mutations, only one homozygous individual has been reported, with no change in phenotype compared with heterozygotes. Here, we describe a novel point mutation in the ZRS, 402C>T (AC007097.4:g.105548C>T), that is transmitted through two Mexican families with one homozygous individual. The homozygous phenotype for this mutation, WMS, is more severe than the numerous heterozygous individuals genotyped from both families who have TPT and PPD. A mouse transgenic enhancer assay shows that this mutation causes an expansion of the enhancer's expression domain in the developing mouse limb, confirming its pathogenicity. Combined, our results identify a novel ZRS mutation in the Mexican population, 402C>T, and suggest that a dosage effect exists for this ZRS mutation.

Clinical and descriptive genetic study of polydactyly: a Pakistani experience of 313 cases

Polydactyly, a common hereditary condition with additional digits in hands and/or feet, is a very attractive model to appreciate clinical and genetic heterogeneity. In order to get an insight into its phenotypic manifestations, we ascertained a cohort of 313 independent families with polydactyly from Pakistan; 35% cases turned out to be familial while 65% were sporadic. In majority of the index cases, polydactyly was presented as an isolated digit defect. Preaxial polydactyly types were 48.24% and postaxial were 51.8%. Familial polydactylies mainly had bilateral and symmetrical presentations, whereas sporadic cases were mostly unilateral and less often symmetrical. In the 313 index subjects a total of 508 limbs with additional digits were recorded. Variable expression was evident as the involvement of upper limbs was more common than the lower, right hand than the left, and left foot than the right. The present cohort establishes interesting epidemiological attributes of polydactyly in the Pakistani population and highlights its extraordinary clinical heterogeneity. Molecular analyses of this cohort are anticipated to elucidate novel genetic factors involved in the origin of additional digits in the growing limb and may provide clues to the role of stochastic factors in the etiology of phenotypic variability in polydactyly.

Epidemiology of isolated preaxial polydactyly type I: Data from the Polish Registry of Congenital Malformations (PRCM)

BackgroundPolydactyly represents a heterogeneous group of congenital hand and foot anomalies with variable clinical features and diverse etiology. Preaxial polydactyly type I (PPD1) is the most frequent form of preaxial polydactyly. The etiology of sporadic PPD1 remains largely unknown and the relative contribution of genetic and environmental factors is not clearly defined. The primary goals of this study are twofold: (1) to examine the epidemiology and clinical features of sporadic PPD1 in comparison to a healthy control group, and (2) to contrast the characteristics of sporadic PPD1 with familial forms of isolated polydactyly.MethodsAmong 2,530,349 live births registered in the Polish Registry of Congenital Malformations (PRCM), we identified 459 children with isolated sporadic PPD1 and 353 children with familial polydactyly, including 57 children with familial PPD1.ResultsIn comparison with the matched group of 303 controls, sporadic PPD1 cases had significantly lower birth order (P = 0.01) and birthweight (P < 0.0001). Similarly, when compared to familial cases of polydactyly, lower birth order (P = 0.047) and lower birthweight (P < 0.0001) were characteristic of sporadic PPD1 cases. Moreover, our analyses suggested several additional risk factors for sporadic PPD1, including lower paternal education levels (P = 0.01), upper respiratory tract infections during the first trimester of pregnancy (P = 0.049), and maternal history of epilepsy (P = 0.01).ConclusionsIn summary, our study provides support to the hypothesis that non-genetic factors play an important role in the etiology of non-familiar PPD1.

Expanded mutational spectrum of the GLI3 gene substantiates genotype–phenotype correlations

Greig cephalopolysyndactyly syndrome (GCPS) and isolated preaxial polydactyly type IV (PPD-IV) are rare autosomal dominant disorders, both caused by mutations in the GLI3 gene. GCPS is mainly characterised by craniofacial abnormalities (macrocephaly/prominent forehead, hypertelorism) and limb malformations, such as PPD-IV, syndactyly and postaxial polydactyly type A or B (PAPA/B). Mutations in the GLI3 gene can also lead to Pallister–Hall syndrome (PHS) and isolated PAPA/B. In this study, we investigated 16 unrelated probands with the clinical diagnosis of GCPS/PPD-IV and found GLI3 mutations in 12 (75 %) of them (nine familial and three sporadic cases). We also performed a detailed clinical evaluation of all 12 GLI3-positive families, with a total of 27 patients. The hallmark triad of GCPS (preaxial polydactyly, macrocephaly/prominent forehead, hypertelorism) was present in 14 cases (52 %), whereas at least one typical dysmorphic feature was manifested in 17 patients (63 %). Upon sequencing of the GLI3 gene, we demonstrated eight novel and two previously reported heterozygous point mutations. We also performed multiplex ligation-dependent probe amplification (MLPA) to screen for intragenic copy number changes and identified heterozygous deletions in the two remaining cases (16.7 %). Our findings fully support previous genotype–phenotype correlations, showing that exonic deletions, missense mutations, as well as truncating variants localised out of the middle third of the GLI3 gene result in GCPS/PPD-IV and not PHS. Additionally, our study shows that intragenic GLI3 deletions may account for a significant proportion of GCPS/PPD-IV causative mutations. Therefore, we propose that MLPA or quantitative polymerase chain reaction (qPCR) should be implemented into routine molecular diagnostic of the GLI3 gene.

Identification of two novel mutations in Shh long-range regulator associated with familial pre-axial polydactyly

Pre-axial polydactyly type II (PPDII, MIM #174500), Werner mesomelic syndrome (MIM %188770) and Haas polysyndactyly (MIM #186200) are a group of closely related conditions caused by mutations in a long-range Sonic hedgehog (SHH, MIM *600725) regulator called ZRS. To date, 19 point mutations, 10 duplications and 1 triplication of the ZRS associated with those pre-axial polydactylies have been reported in humans, mice, cats and chickens. Some of these have been shown to cause ectopic expression of Shh in the limb bud in mice, leading to a polydactylous phenotype, but the precise mechanism by which ZRS mutations generate this phenotype remains unknown. We present two PPDII families with fully penetrant point mutations in ultra-conserved predicted binding sites for transcription factors SOX9 and PAX3, two possible candidates for regulating SHH expression. Screening for point mutations or copy-number variation of the ZRS, high-resolution array-CGH, and screening of other conserved non-coding sequences (CNS) surrounding SHH in a third family are negative. This is the sixth PPDII pedigree with possible linkage to 7q36 that presents with no detectable ZRS mutation. We hypothesize that another nearby regulatory sequence, or an undetected position effect between ZRS and SHH, could be responsible for negative familial cases linked to 7q36.

Metopic craniosynostosis due to mutations inGLI3: A novel association

We report on the novel association of trigonocephaly and polysyndactyly in two unrelated patients due to mutations within the last third (exon 14) and first third (exon 6) of the GLI3 gene, respectively. GLI3 acts as a downstream mediator of the Sonic hedgehog signal-transduction pathway which is essential for early development; and plays a role in cell growth, specialization, and patterning of structures such as the brain and limbs. GLI3 mutations have been identified in patients with Pallister-Hall, Grieg cephalopolysyndactyly syndrome (GCPS), postaxial polydactyly type A1, preaxial polydactyly type IV, and in one patient with acrocallosal syndrome (ACLS). Furthermore, deletions including the GLI3 gene have been reported in patients with features of GCPS and ACLS. To date, trigonocephaly has not been associated with abnormalities of GLI3 and craniosynostosis is not a feature of GCPS. However, Hootnick and Holmes reported on a father with polysyndactyly and son with trigonocephaly, polysyndactyly, and agenesis of the corpus callosum, considered GCPS thereafter. Guzzetta et al. subsequently described a patient with trigonocephaly, polysyndactyly, and agenesis of the corpus callosum postulating a diagnosis of GCPS, later considered ACLS. In retrospect, these two patients, evaluated prior to mutational analysis, and our patients, with confirmed mutations, likely fall within the GLI3 morphopathy spectrum and may provide a bridge to better understanding those patients with overlapping features of GCPS and ACLS. Based on this observation, we suggest GLI3 studies in patients presenting with this constellation of findings, specifically metopic craniosynostosis with polysyndactyly, in order to provide appropriate medical management and genetic counseling.

A specific mutation in the distant sonic hedgehog (SHH)cis-regulator (ZRS) causes Werner mesomelic syndrome (WMS) while complete ZRS duplications underlie Haas type polysyndactyly and preaxial polydactyly (PPD) with or without triphalangeal thumb

Werner mesomelic syndrome (WMS) is an autosomal dominant disorder with unknown molecular etiology characterized by hypo- or aplasia of the tibiae in addition to the preaxial polydactyly (PPD) of the hands and feet and/or five-fingered hand with absence of thumbs. We show that point mutations of a specific nucleotide within the sonic hedgehog (SHH) regulatory region (ZRS) cause WMS. In a previously unpublished WMS family, we identified the causative G>A transition at position 404 of the ZRS, and in six affected family members of a second WMS family we found a 404G>C mutation of the ZRS. The 404G>A ZRS mutation is known as the "Cuban mutation" of PPD type II (PPD2). Interestingly, the index patient of that family had tibial hypoplasia as well. These data provide the first evidence that WMS is caused by a specific ZRS mutation, which leads to strong ectopic SHH expression. In contrast, we show that complete duplications of the ZRS region lead to type Haas polysyndactyly or triphalangeal thumb-polysyndactyly syndrome, but do not affect lower limb development. We suggest the term "ZRS-associated syndromes" and a clinical subclassification for the continuum of limb malformations caused by different molecular alterations of the ZRS.

A and B preaxial polydactyly with syndactyly of feet and hands in the same person — a case report

Preaxial polydactyly of the hand is more common than postaxial polydactyly and postaxial polydactyly of the foot is more common than preaxial in white patients. Syndactyly is commonly regarded as next in frequency among the congenital hand deformities. Preaxial polydactyly of the feet and hands and polydactyly type A and B with syndactyly in the same individual is a rare condition. In this work we present this rare disorder in male infant. The physical and X-ray examinations showed preaxial polydactyly type A of both hands and A and B polydactyly with syndactyly of feet.

The Greig cephalopolysyndactyly syndrome

The Greig cephalopolysyndactyly syndrome (GCPS) is a pleiotropic, multiple congenital anomaly syndrome. It is rare, but precise estimates of incidence are difficult to determine, as ascertainment is erratic (estimated range 1–9/1,000,000). The primary findings include hypertelorism, macrocephaly with frontal bossing, and polysyndactyly. The polydactyly is most commonly preaxial of the feet and postaxial in the hands, with variable cutaneous syndactyly, but the limb findings vary significantly. Other low frequency findings include central nervous system (CNS) anomalies, hernias, and cognitive impairment.GCPS is caused by loss of function mutations in the GLI3 transcription factor gene and is inherited in an autosomal dominant pattern. The disorder is allelic to the Pallister-Hall syndrome and one form of the acrocallosal syndrome.Clinical diagnosis is challenging because the findings of GCPS are relatively non-specific, and no specific and sensitive clinical have been delineated. For this reason, we have proposed a combined clinical-molecular definition for the syndrome. A presumptive diagnosis of GCPS can be made if the patient has the classic triad of preaxial polydactyly with cutaneous syndactyly of at least one limb, hypertelorism, and macrocephaly. Patients with a phenotype consistent with GCPS (but which may not manifest all three attributes listed above) and a GLI3 mutation may be diagnosed definitively with GCPS. In addition, persons with a GCPS-consistent phenotype who are related to a definitively diagnosed family member in a pattern consistent with autosomal dominant inheritance may be diagnosed definitively as well. Antenatal molecular diagnosis is technically straightforward to perform.Differential diagnoses include preaxial polydactyly type 4, the GCPS contiguous gene syndrome, acrocallosal syndrome, Gorlin syndrome, Carpenter syndrome, and Teebi syndrome.Treatment of the disorder is symptomatic, with plastic or orthopedic surgery indicated for significant limb malformations.The prognosis for typically affected patients is excellent. There may be a slight increase in the incidence of developmental delay or cognitive impairment. Patients with large deletions that include GLI3 may have a worse prognosis.The Article is a work of the United States Government. Title 17 U.S.C 5 105 provides that copyright protection is not available for any work of the United States Government in the United States. The United States hereby grants to anyone a paid-up, nonexclusive, irrevocable worldwide license to reproduce, prepare derivative works, distribute copies to the public and perform publicly and display publicly the work, and also retains the nonexclusive right to do all of the above for or on behalf of the United States.

Triphalangeal thumb–polysyndactyly syndrome and syndactyly type IV are caused by genomic duplications involving the long range, limb-specific SHH enhancer

Background:The Sonic hedgehog (SHH) protein produced in the zone of polarising activity (ZPA) is a major determinant of the identity and numbers of digits in early limb development. Preaxial polydactyly...