Weiwen Guo

DAX1 Mutations Map to Putative Structural Domains in a Deduced Three-Dimensional Model

The DAX1 protein is an orphan nuclear hormone receptor based on sequence similarity in the putative ligand-binding domain (LBD). DAX1 mutations result in X-linked adrenal hypoplasia congenita (AHC). Our objective was to identify DAX1 mutations in a series of families, to determine the types of mutations resulting in AHC and to locate single-amino-acid changes in a DAX1 structural model. The 14 new mutations identified among our 17 families with AHC brought the total number of families with AHC to 48 and the number of reported mutations to 42; 1 family showed gonadal mosaicism. These mutations included 23 frameshift, 12 nonsense, and six missense mutations and one single-codon deletion. We mapped the seven single-amino-acid changes to a homology model constructed by use of the three-dimensional crystal structures of the thyroid-hormone receptor and retinoid X receptor alpha. All single-amino-acid changes mapped to the C-terminal half of the DAX1 protein, in the conserved hydrophobic core of the putative LBD, and none affected residues expected to interact directly with a ligand. We conclude that most genetic alterations in DAX1 are frameshift or nonsense mutations and speculate that the codon deletion and missense mutations give insight into the structure and function of DAX1.

Ahch, the mouse homologue of DAX1: cloning, characterization and synteny with GyK, the glycerol kinase locus.

We cloned the murine full-length cDNA encoding Ahch, the mouse homologue of DAX1 (DSS-AHC Region on Human X Chromosome, Gene1) which is the gene responsible for human X-linked adrenal hypoplasia congenita (AHC) and hypogonadotropic hypogonadism (HH). Sequence analysis revealed that the murine and human cDNAs have 65% aa identity and 75% aa similarity overall. The cysteine residues in the putative DNA binding domain, which may interact with Zn2+ ions to form zinc fingers, are 100% conserved between the two species, indicating that the novel zinc-finger structures in DAX1 may be functional. In addition, mouse interspecific backcrosses show that the Ahch gene is closely linked to the glycerol kinase locus, GyK, on the mouse X chromosome, indicating that the order of the loci is conserved in this syntenic region between mouse and human.

Glycerol Kinase Missense Mutations Provide Structure-Function But Not Genotype-Phenotype Insights. † 641

Glycerol Kinase Missense Mutations Provide Structure-Function But Not Genotype-Phenotype Insights. † 641

Complex glycerol kinase deficiency: A contiguous gene syndrome involving the Duchenne muscular dystrophy, glycerol kinase, and adrenal hypoplasia congenita loci

Complex glycerol kinase deficiency is a contiguous gene syndrome that involves deletion of the glycerol kinase (GK) gene along with the loci for Duchenne muscular dystrophy (DMD) and/or adrenal hypoplasia congenita (AHC). The deletion breakpoints in these patients allowed identification of the critical regions for the GK and AHC genes, and both were identified using a positional cloning strategy. In addition to complex glycerol kinase deficiency, there are also two distinct phenotypes characterizing isolated glycerol kinase deficiency, the juvenile and benign forms. The juvenile form has onset in the first weeks to years of life with episodic decompensation. These episodes can be prevented or at least reduced in number by the use of a reduced-fat and therefore reduced-glycerol diet. Other families exhibit the benign form of isolated glycerol kinase deficiency. The affected individuals within these families have the biochemical features of this disorder but are asymptomatic.