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.
Pathogenic mutations in the GLI3 gene (glioma-associated oncogene family zinc finger 3) have been associated with both nonsyndromic and syndromic polydactyly.
Pathogenic mutations in the GLI3 gene (glioma-associated oncogene family zinc finger 3) have been associated with both nonsyndromic and syndromic polydactyly.
We also present a review of GLI3-associated isolated limb anomalies, which indicates that GLI3 mutation leads primarily to two well-established polydactyly types: postaxial types A and B and crossed polydactyly type I.
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.
The GLI3 gene exhibits allelic heterogeneity as mutations in this gene are associated with several developmental syndromic and non-syndromic polydactyly.
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.
In conjunction, we observed Gata6 and Gli3 genetically interact, and compound heterozygous mutants develop preaxial polydactyly without ectopic Shh expression, indicating an additional prior mechanism to prevent polydactyly.
Interestingly, GLI3 and SHH (ZRS/SHH enhancer), two antagonistic factors known to modulate digit number and identity during development, have also been implicated in polydactyly.
Genotype-phenotype correlation studies of GLI3 mutations suggest a model by which mutations in the zinc-finger domain (ZFD) of GLI3 likely lead to syndromic polydactyly.
A single patient with acrocallosal syndrome and a de novo p.Ala934Pro mutation in GLI3 has been reported, whereas diverse and numerous GLI3 mutations have also been described in syndromes with overlapping clinical manifestations, including Greig cephalopolysyndactyly syndrome, Pallister-Hall syndrome, trigonocephaly with craniosynostosis and polydactyly, oral-facial-digital syndrome, and non-syndromic polydactyly.
Genetic polydactyly mice such as Pdn/Pdn (Polydactyly Nagoya), Xt(H)/Xt(H) (Extra toes) and Xt(J)/Xt(J) (Extra toes Jackson) are the mouse homolog of GCPS, and Gli3(tmlUrtt)/Gli3(tmlUrt) is produced as the mouse homolog of PHS.
This includes 19 probands (12 mutations) who fulfilled clinical criteria for GCPS or PHS, 48 probands (16 mutations) with features of GCPS or PHS but who did not meet the clinical criteria (sub-GCPS and sub-PHS), 21 probands (6 mutations) with features of PHS or GCPS and oral-facial-digital syndrome, and 5 probands (1 mutation) with nonsyndromic polydactyly.
We performed mutational analysis in the four main HPE causing genes (SHH, SIX3, TGIF, and ZIC2) and GLI3, a gene associated with polydactyly as well as fluorescent in situ hybridization (FISH) to search for microdeletions in these genes and two candidate HPE genes (DISP1 and FOXA2).
The gene responsible for the polydactyly/arhinencephaly (Pdn/Pdn) mouse, which exhibits polysyndactyly and arhinencephaly and has a 13.2% risk of neural tube defects (NTD), has been identified as Gli3.
Since FBXW11 is relatively highly expressed in fetal brain and is directly involved in proteolytic processing of GLI3, we propose FBXW11 as the most likely candidate gene for the HPE and prexial polydactyly phenotype.
In addition to GCPS, Pallister-Hall syndrome (PHS; MIM 146510) and post-axial polydactyly type A (PAP-A; MIM 174200), two other disorders of human development, are caused by GLI3 mutations.