Hallux valgus interphalangeus and a novel mutation in HOXA13. Part of the broadening spectrum of Hand-Foot-Genital syndrome

Hand-foot-genital syndrome due to a duplication variant in the GC-rich region of HOXA13

BACKGROUND

Hand-Foot-Genital Syndrome (HFGS) is an autosomal dominant disorder characterized by a broad phenotypic spectrum. Variants in HOXA13 gene were associated with HFGS. To date, only twenty families with HFGS have been reported. However, the challenge in HFGS is the limited sample sizes and phenotypic heterogeneity. The advent of next-generation sequencing has permitted the identification of patients with HOXA13 variants who do not manifest with the full HFGS syndromic features.

METHODS

Trio (parents-proband) Whole-exome sequence(WES) and whole-genome sequencing(WGS) was carried out in this study to investigate the underlying pathogenic genetic factor of the neonate with a wide variety of clinical abnormalities.

RESULTS

No possible pathogenetic variation was detected by trio-WES, and a duplication variant in HOXA13 (c.360_377dup, p.Ala128_Ala133dup), inherited from her mother, was identified by the subsequent WGS in the proband with malnutrition, feeding difficulties, electrolyte disorders, metabolic acidosis, recurrent urinary tract infections, hydronephrosis, nephrolithiasis, abnormal ureter morphology, cholelithiasis, uterus didelphys. Sequence analysis of the variant region (exon1) indicated a high GC content of 73.92%. In addition, further enquiry of the family history revealed that 5 members of the family in 4 generations had hand and foot anomalies.

CONCLUSION

The neonate was diagnosed with HFGS by genetic analysis. GC content had less influence on sequence coverage in WGS than WES analysis. This was the first report of trio-WGS study for HFGS genetic diagnosis, revealed that subsequent WGS was necessary for identification of potentially pathogenic variants in unexplained genetic disorders.

Hallux Valgus Interphalangeus with Large Ossicle Formation: A Case Report

Hallux valgus interphalangeus (HVIP) is a deviation of the distal phalanx in relation to the proximal phalanx. Its etiology is considered multifactorial, including growth development disturbances, external pressure, and biomechanical alteration involving the interphalangeal joint. Here, we report a case of HVIP with the presence of a large ossicle at the lateral side, which was considered related to HVIP development. A 21-year-old woman presented HVIP that had developed since childhood. She complained of pain in her right great toe that worsened in the previous several months, particularly when walking and wearing shoes. Surgical correction consisted of Akin osteotomy, fixation with headless screw, ossicle excision, and medial capsulorrhaphy. The interphalangeal joint angle was improved from 28.69⁰ pre-operatively to 8.93⁰ post-operatively. The wound healed uneventfully and the patient was satisfied. Akin osteotomy with concomitant ossicle excision was effective in this case. Gaining more knowledge regarding ossicles around the foot will provide a better understanding of deformity correction, especially from the biomechanical standpoint.

Morphology of the first metatarsal head as a risk factor for hallux valgus interphalangeus

BACKGROUND

The aetiology of hallux valgus interphalangeus (HVI) is not well understood. First metatarsophalangeal joint stability, influenced by first metatarsal head shape, may be linked to HVI. We hypothesised that first metatarsal head shape is a risk factor for HVI. No published article could be found in the literature investigating this hypothesis.

METHODS

127 standardised foot radiographs were analysed retrospectively. The hallux valgus angle (HVA) and interphalangeus angle (IPA) were measured. The first metatarsal head shape was divided into chevron, round and flat groups. Statistical analysis was then performed to investigate the relationship between first metatarsal head shape and the occurrence of HVI.

RESULTS

There was no statistically significant relationship between first metatarsal head shape and the occurrence of HVI. There was however a negative relationship between HVA and HVI.

CONCLUSIONS

The morphology of the first metatarsal head does not seem to be a risk factor for HVI. A known negative relationship between HVA and IPA is reinforced.

LEVEL OF EVIDENCE

Level III, retrospective cohort.

Distal Akin osteotomy for hallux valgus interphalangeus

BACKGROUND

The aim of this study was to assess clinical and radiological outcomes in patients who underwent distal Akin osteotomy for hallux valgus interphalangeus (HVI).

METHODS

A series of 15 consecutive patients (17 feet) was retrospectively reviewed. All the patients were preoperatively and post-operatively evaluated with a physical and radiographic assessment (HVI angle). Satisfaction has been assessed through a satisfaction survey, the scale used consisted in three possible choice: very satisfied, satisfied, not satisfied.

RESULTS

Among 15 patients the 52.9% (9 patients) stated to be "very satisfied", the 41.2% (7 patients) "satisfied" and just a 5.9% (one patient) was "not satisfied". The mean HVI value decreased from 24.9°±7.8° preoperatively to 13.1°±5.8° postoperatively at last follow up (p<0.05).

CONCLUSIONS

Based on these findings we can conclude that the distal Akin osteotomy can be considered safe and effective in the surgical correction of symptomatic HVI deformities.

7p15 deletion as the cause of hand-foot-genital syndrome: a case report, literature review and proposal of a minimum region for this phenotype

Background

Hand-foot-genital syndrome (HFGS) is a rare condition characterized by congenital malformations in the limbs and genitourinary tract. Generally, this syndrome occurs due to point mutations that cause loss of function of the HOXA13 gene, which is located on 7p15; however, there are some patients with HFGS caused by interstitial deletions in this region.

Case presentation

We describe a pediatric Mexican patient who came to the Medical Genetics Department at the National Institute of Pediatrics because he presented with genital, hand and feet anomalies, facial dysmorphisms, and learning difficulties. Array CGH reported a 12.7 Mb deletion that includes HOXA13.

Conclusions

We compared our patient with cases of HFGS reported in the literature caused by a microdeletion; we found a minimum shared region in 7p15.2. By analyzing the phenotype in these patients, we suggest that microdeletions in this region should be investigated in all patients with clinical characteristics of HFGS who also present with dysplastic ears, mainly low-set implantation with a prominent antihelix, as well as a low nasal bridge and long philtrum.

A missense mutation of HOXA13 underlies hand-foot-genital syndrome in a Chinese family

Hand-foot-genital syndrome (HFGS) is a rare autosomal dominant inherited syndrome characterized by limb malformations and urogenital defects. HFGS is caused by mutations in the HOXA13 gene. The aim of this study was to identify causative mutations in individuals and to explore the molecular pathogenesis in a Chinese family with HFGS. We performed Sanger sequencing and identified a recurrent missense mutation in the homeodomain (c.1123G>T, p.V375F) of HOXA13, molecular modelling predicted the mutation would affect DNA binding, and a luciferase reporter assay indicated that it impaired the ability of HOXA13 to activate transcription of the human EPHA7 promoter. This is the first report of the molecular basis for HFGS caused by missense mutations of HOXA13.

Etiologies of uterine malformations

Ranging from aplastic uterus (including Mayer-Rokitansky-Kuster-Hauser syndrome) to incomplete septate uterus, uterine malformations as a group are relatively frequent in the general population. Specific causes remain largely unknown. Although most occurrences ostensibly seem sporadic, familial recurrences have been observed, which strongly implicate genetic factors. Through the study of animal models, human syndromes, and structural chromosomal variation, several candidate genes have been proposed and subsequently tested with targeted methods in series of individuals with isolated, non-isolated, or syndromic uterine malformations. To date, a few genes have garnered strong evidence of causality, mainly in syndromic presentations (HNF1B, WNT4, WNT7A, HOXA13). Sequencing of candidate genes in series of individuals with isolated uterine abnormalities has been able to suggest an association for several genes, but confirmation of a strong causative effect is still lacking for the majority of them. We review the current state of knowledge about the developmental origins of uterine malformations, with a focus on the genetic variants that have been implicated or associated with these conditions in humans, and we discuss potential reasons for the high rate of negative results. The evidence for various environmental and epigenetic factors is also reviewed. © 2016 Wiley Periodicals, Inc.

Dual genetic diagnoses: Atypical hand-foot-genital syndrome and developmental delay due to de novo mutations in HOXA13 and NRXN1

We describe a male patient with dual genetic diagnoses of atypical hand-foot-genital syndrome (HFGS) and developmental delay. The proband had features of HFGS that included bilateral vesicoureteric junction obstruction with ectopic ureters, brachydactyly of various fingers and toes, hypoplastic thenar eminences, and absent nails on both 4th toes and right 5th toe. The atypical features of HFGS present were bilateral hallux valgus malformations and bilateral preaxial polydactyly of the hands. Chromosomal microarray analysis identified a de novo 0.5 Mb deletion at 2p16.3, including the first four exons of the NRXN1 gene. Whole exome sequencing and subsequent Sanger sequencing identified a de novo missense mutation (c.1123G>T, p.Val375Phe) in exon 2 of the HOXA13 gene, predicted to be damaging and located in the homeobox domain. The intragenic NRXN1 deletion is thought to explain his developmental delay via a separate genetic mechanism.

A new hereditary congenital facial palsy case supports arg5 in HOX-DNA binding domain as possible hot spot for mutations

Moebius syndrome (MBS) is a rare congenital disorder characterized by rhombencephalic mal development, mainly presenting with facial palsy with limited gaze abduction. Most cases are sporadic, possibly caused by a combination of environmental and genetic factors; however, no proven specific associations have been yet established. Hereditary congenital facial palsy (HCFP) is an autosomal dominant congenital dysinnervation syndrome, recognizable by the isolated dysfunction of the seventh cranial nerve. Mutant mice for Hoxb1 were reported to present with facial weakness, resembling MBS. Recently a homozygous mutation altering arg5 residue of HOXB1 homeodomain into cys5 was identified in two families with HCFP. We screened 95 sporadic patients diagnosed as MBS or HCFP for mutations in HOXB1. A novel homozygous alteration was identified in one HCFP case, affecting the same residue, resulting to his5. In silico protein analysis predicted stronger HOXB1-DNA binding properties for his5 than cys5 that resulted to milder phenotype. It should be noted that, inclusive of the previous report, only two mutations revealed in HOXB1 associated with HCFP involved the same amino acid arg5 in HOXB1 residing in HOXB1-DNA-PBX1 ternary complex.

Severe manifestations of hand-foot-genital syndrome associated with a novel HOXA13 mutation

We report on a girl with absent nails, short/absent distal phalanges of the second to fifth fingers and toes, short thumbs, absent halluces, and carpo-tarsal coalition who also had genitourinary malformations. Trio-based whole exome sequencing identified a novel de novo mutation (c.1102A>T, p.Ile368Phe) in the HOXA13 gene. Heterozygous HOXA13 mutations have been previously reported in hand-foot-genital syndrome and Guttmacher syndrome, which are variably associated with small nails, short distal and middle phalanges, short thumbs and halluces, but not absent nails. Considering the molecular data, the phenotype in the present patient was defined as the severe end of hand-foot-genital and Guttmacher syndrome spectrum. Our observation expands the clinical spectrum caused by heterozygous HOXA13 mutations and reinforces the difficulty of differential diagnosis on clinical grounds for the disorders with short distal phalanges, short thumbs, and short halluces.

Hallux abductus interphalangeus in normal feet, early-stage hallux limitus, and hallux valgus

BACKGROUND

Excessive deviation of the distal phalanx in abduction frequently occurs in advanced stages of hallux rigidus but not in hallux valgus. Therefore, theoretically there should be no significant differences in the hallux interphalangeal angle (HIPA) between individuals with normal feet, those with hallux valgus, and those with mild hallux limitus. The objective of the present study was thus to determine if significant differences in HIPA exist in the early stages of hallux valgus or hallux limitus deformities.

METHODS

The hallux interphalangeal angle was measured in three groups of participants: a control group with normal feet (45 participants), a hallux valgus group (49 participants), and a hallux limitus group (48 participants). Both of the pathologies were at an early stage. A dorsoplantar radiograph under weightbearing conditions was taken for each individual, and measurements (HIPA and hallux abductus angle [HAA]) were taken using AutoCAD (Autodesk Inc, San Rafael, California) software. Intergroup comparisons of HIPA, and correlations between HIPA, HAA, and hallux dorsiflexion were calculated.

RESULTS

The comparisons revealed no significant differences in the values of HIPA between any of the groups (15.2 ± 5.9 degrees in the control group, 15.5 ± 3.9 degrees in the hallux valgus group, and 16.15 ± 4.3 in the hallux limitus group; P  =  0.634). The Pearson correlation coefficients in particular showed no correlation between hallux dorsiflexion, HAA, and HIPA.

CONCLUSIONS

For the study participants, there were similar deviations of the distal phalanx of the hallux with respect to the proximal phalanx in normal feet and in feet with the early stages of the hallux limitus and hallux valgus deformities.

Structural basis for sequence specific DNA binding and protein dimerization of HOXA13

The homeobox gene (HOXA13) codes for a transcription factor protein that binds to AT-rich DNA sequences and controls expression of genes during embryonic morphogenesis. Here we present the NMR structure of HOXA13 homeodomain (A13DBD) bound to an 11-mer DNA duplex. A13DBD forms a dimer that binds to DNA with a dissociation constant of 7.5 nM. The A13DBD/DNA complex has a molar mass of 35 kDa consistent with two molecules of DNA bound at both ends of the A13DBD dimer. A13DBD contains an N-terminal arm (residues 324 – 329) that binds in the DNA minor groove, and a C-terminal helix (residues 362 – 382) that contacts the ATAA nucleotide sequence in the major groove. The N370 side-chain forms hydrogen bonds with the purine base of A5* (base paired with T5). Side-chain methyl groups of V373 form hydrophobic contacts with the pyrimidine methyl groups of T5, T6* and T7*, responsible for recognition of TAA in the DNA core. I366 makes similar methyl contacts with T3* and T4*. Mutants (I366A, N370A and V373G) all have decreased DNA binding and transcriptional activity. Exposed protein residues (R337, K343, and F344) make intermolecular contacts at the protein dimer interface. The mutation F344A weakens protein dimerization and lowers transcriptional activity by 76%. We conclude that the non-conserved residue, V373 is critical for structurally recognizing TAA in the major groove, and that HOXA13 dimerization is required to activate transcription of target genes.