Split hand/split foot, iris/choroid coloboma, hypospadias and subfertility: a new developmental malformation syndrome?

Positive regulation of steroidogenic acute regulatory protein gene expression through the interaction between Dlx and GATA-4 for testicular steroidogenesis

Split hand/foot malformation (SHFM) is syndromic ectrodactyly often associated with mental retardation and/or craniofacial defects. Several clinical reports previously described urogenital dysplasia such as micropenis, hypospadias, and small testis in SHFM patients. Genetic lesions in the Dlx5 and Dlx6 (Dlx5/6) locus are associated with the human genetic disorder SHFM type 1. Although Dlx5/6 are expressed in the testis, their possible function of Dlx5/6 during testis differentiation has not been described. In this study, we show that Dlx5/6 are expressed in the fetal Leydig cells during testis development. We examined the effect of Dlx5 expression on the promoter activation of the steroidogenic acute regulatory protein (StAR) gene, which is essential for gonadal and adrenal steroidogenesis, in a Leydig cell line. Dlx5 efficiently activates the StAR promoter when GATA-4, another transcription factor essential for testicular steroidogenesis, was coexpressed. The transcriptional activation required the GATA-4-recognition element in the StAR promoter region and Dlx5 can physically interact with GATA-4. Furthermore, we herein show that the double inactivation of Dlx5 and Dlx6 in the mouse leads to decreased testosterone level and abnormal masculinization phenotype. These results suggest that Dlx5 and Dlx6 participate in the control of steroidogenesis during testis development. The findings of this study may open the way to analyze human congenital birth defects.

Abnormal urethra formation in mouse models of split-hand/split-foot malformation type 1 and type 4

Urogenital birth defects are one of the common phenotypes observed in hereditary human disorders. In particular, limb malformations are often associated with urogenital developmental abnormalities, as the case for Hand-foot-genital syndrome displaying similar hypoplasia/agenesis of limbs and external genitalia. Split-hand/split-foot malformation (SHFM) is a syndromic limb disorder affecting the central rays of the autopod with median clefts of the hands and feet, missing central fingers and often fusion of the remaining ones. SHFM type 1 (SHFM1) is linked to genomic deletions or rearrangements, which includes the distal-less-related homeogenes DLX5 and DLX6 as well as DSS1. SHFM type 4 (SHFM4) is associated with mutations in p63, which encodes a p53-related transcription factor. To understand that SHFM is associated with urogenital birth defects, we performed gene expression analysis and gene knockout mouse model analyses. We show here that Dlx5, Dlx6, p63 and Bmp7, one of the p63 downstream candidate genes, are all expressed in the developing urethral plate (UP) and that targeted inactivation of these genes in the mouse results in UP defects leading to abnormal urethra formation. These results suggested that different set of transcription factors and growth factor genes play similar developmental functions during embryonic urethra formation. Human SHFM syndromes display multiple phenotypes with variations in addition to split hand foot limb phenotype. These results suggest that different genes associated with human SHFM could also be involved in the aetiogenesis of hypospadias pointing toward a common molecular origin of these congenital malformations.

Split hand malformation, hypospadias, microphthalmia, distinctive face and short stature in two brothers suggest a new syndrome

Split hand/foot malformation (SHFM) is a genetically heterogeneous limb malformation that may be isolated or associated with other malformations. More than 50 recognizable entities with SHFM have been described and at least 5 mapped genetic loci have been implicated. Two brothers with intrauterine growth retardation, short stature, distinctive face, microphthalmia, genital anomalies, and SHFM are described. Molecular analyses of TP63, HOXA13, and HOXD13 genes were normal. We propose this pattern to be a newly recognized SHFM syndrome.