X-Linked Adrenal Hypoplasia Congenita in a Boy due to a Novel Deletion of the Entire NR0B1 (DAX1) and MAGEB1–4 Genes

Figure 1

(a) Schematic representation of NR0B1 (DAX1) gene localisation in the Xp21 region of the X chromosome between the IL1RAPL1 and dystrophin (DMD) genes. IL1RAPL1 encodes for a putative transmembrane cytokine receptor related to receptors and receptor accessory proteins for interleukin 1 and interleukin 18 and is expressed in the brain and muscles. The MAGEB (melanoma antigen family B) gene cluster encompasses the MAGEB1, B2, B3, and B4 genes, which are expressed in tumor cells but are silent in normal adult tissues except for the male germ line cells. NR0B1 (DAX1), GK: glycerol kinase gene, FTHL17: the testis specific ferritin heavy chain gene, and DMD: dystrophin gene. (b) Genomic structure of the NR0B1 (DAX1) gene composed of two exons (exon 1 and 2). Alternatively spliced exon 2α located within the intron is also shown. (c) Functional domain structure of the NR0B1 (DAX1) protein. NR0B1 (DAX1) protein has 470 amino acids and belongs to the nuclear hormone receptor superfamily. NR0B1 (DAX1) displays a novel DNA-binding domain at its amino terminus. This N-terminal repeat region with LXXLL motifs is crucial for protein-protein interactions. The three total repeats and fourth incomplete repeat of a 65- to 67-amino acid sequence, rich in alanine and glycine, are indicated by arrows. The C-terminal part of the NR0B1 (DAX1) protein shows the characteristics of a nuclear hormone receptor ligand-binding domain (LBD) and functions as a transcriptional repression domain. (d) PCR analysis of the NR0B1 (DAX1) gene results. M: DNA molecular weight 50 bp marker (Sigma), lanes 1-2: no amplification of exon 1 in the patient, lanes 3-4: amplification of exon 1 in patient’s mother, lanes 5-6: amplification of exon 2 in the patient, lanes 7-8: amplification of exon 2 in the patient’s mother, and K−: negative control without genomic DNA. Exon 1 was not amplified in the patient, suggesting NR0B1 (DAX1) deletion. The higher band that should correspond to exon 2 of NR0B1 (DAX1), based on BLASTn analysis, was similar to chromosome 7. This band was not observed in the patient’s mother in whom PCR product of the expected length was amplified (lanes 3-4). (e) Array comparative genomic hybridization (aCGH) results showing a ~300 kb hemizygous deletion on X chromosome encompassing the entire coding sequences of the NR0B1 (DAX1) and MAGEB genes. Genomic coordinates delineating minimal size of the detected loss according to UCSC genome build HG18 are as follows: chrX: 30017532–30301543. The deletion does not involve neighbouring genes such as GK, DMD, and IL1RAPL1.

(a) NR0B1 (DAX1) gene genomic localisation

(b) NR0B1 (DAX1) gene genomic structure

(c) NR0B1 (DAX1) protein structure

(d) PCR results

(e) Array CGH results, microdeletion region