New insights into genotype-phenotype correlation for GLI3 mutations

Abstract

The phenotypic spectrum of GLI3 mutations includes autosomal dominant Greig cephalopolysyndactyly syndrome (GCPS) and Pallister-Hall syndrome (PHS). PHS was first described as a lethal condition associating hypothalamic hamartoma, postaxial or central polydactyly, anal atresia and bifid epiglottis. Typical GCPS combines polysyndactyly of hands and feet and craniofacial features. Genotype-phenotype correlations have been found both for the location and the nature of GLI3 mutations, highlighting the bifunctional nature of GLI3 during development. Here we report on the molecular and clinical study of 76 cases from 55 families with either a GLI3 mutation (49 GCPS and 21 PHS), or a large deletion encompassing the GLI3 gene (6 GCPS cases). Most of mutations are novel and consistent with the previously reported genotype-phenotype correlation. Our results also show a correlation between the location of the mutation and abnormal corpus callosum observed in some patients with GCPS. Fetal PHS observations emphasize on the possible lethality of GLI3 mutations and extend the phenotypic spectrum of malformations such as agnathia and reductional limbs defects. GLI3 expression studied by in situ hybridization during human development confirms its early expression in target tissues.

Figure 1

Schematic representation of GLI3 domains and localization of the GLI3 mutations reported in this study. Red bars at the nucleotides 1998 and 3481 divide the gene into three segments, limiting the PHS region as described elsewhere. The colored boxes within GLI3 represent the seven regions of similarity between human GLI proteins originally defined by Ruppert et al. ZNF: zinc-finger domain (aa 462–645), PC: proteolytic cleavage site, TA1 (aa 1376–1580) and TA2 (aa 1044–1322): two independent transactivation domains as described by Kalff-Suske et al.¹¹ Mutations written in red: PHS patients with severe phenotypes; in green: GCPS cases with abnormal corpus callosum; black bars: truncating nonsense and frameshift mutations; purple bar: splice mutation; blue bars: missense mutations. A full color version of this figure is available at the European Journal of Human Genetics journal online.

Figure 2

Photographs and radiographies of GCPS cases with identified GLI3 mutation. (a, b) Preaxial polysyndactyly in the feet with a broad first metacarpal on X-rays (G076, G14083). (c) Broad hallux and syndactyly (G16012, daughter). (d) Preaxial polysyndactyly (G16012). (e) Bifid terminal phalanx of the thumb (G14083). (f) Heptadactyly (preaxial and postaxial PD, G15198). (g) Broad thumbs (G16012, daughter). (h) Broad thumb and postaxial PD type (b) (G16012).

Figure 3

Photographs, radiographies and histological findings of PHS cases with identified GLI3 mutation. (a) Insertional PD and syndactyly (G072). (b) Oligodactyly (G080). (c) Insertional PD with a supernumerary metacarpal (G072). (d) Y-shaped metacarpal without PD (P15112). (e) Brain MRI showing a HH (P15112). (f) HH on neuropathological examination (G013). (g) Agnathia, hypoplastic maxillary, absence of oral orifice and oligosyndactyly (G012). (h) X-rays of G012 showing oligosyndactyly of hands and feet, arthrogryposis, mesomelia, bilateral radio-ulnar bowing, absence of tibia and fibula (G012). (i) (G024) and (j) (G080) showing micrognathia, micromelia, oligosyndactyly and club feet.

Figure 4

In situ hybridization of GLI3 during human development. (a, b) CS 15; (c, d) CS 19. (b, d) Slides hybridized with an antisense GLI3 probe. (a, c) Adjacent slides respectively to (b) and (d) stained with HES. In addition to the expression in central nervous system (prosencephalon (pr), rhombencephalon (rh) neural tube (nt)), limb bud (lb), pituitary gland (p, arrowhead) and kidney (K), a signal was observed in human pharyngeal arches (pa1) then in mandible (mn) and maxillary (mx) (red arrows). A full color version of this figure is available at the European Journal of Human Genetics journal online.