Recent data implicate locally produced steroids, termed neurosteroids, as regulators of neuronal function. Adrenal and gonadal steroidogenesis is controlled by changes in the steroidogenic acute regulatory protein (StAR); however, little is known about the regulation of neurosteroid production. We now demonstrate unequivocally that StAR mRNA and protein are expressed within glia and neurons in discrete regions of the mouse brain, and that glial StAR expression is inducible. Consistent with a role in de novoneurosteroidogenesis, StAR colocalizes with the cholesterol side-chain cleavage enzyme P450_scc in both mouse and human brains. These data support a role for StAR in the production of neurosteroids and identify potential sites of active de novo steroid synthesis in the brain.

Context: Cytochrome P450 oxidoreductase (POR) deficiency is a rare autosomal recessive disorder characterized by skeletal dysplasia, adrenal dysfunction, disorders of sex development (DSD), and maternal virilization during pregnancy. Although multiple studies have been performed for this condition, several matters remain to be clarified, including the presence of manifesting heterozygosity and the underlying factors for clinical variability. Objective: The objective of the study was to examine such unresolved matters by detailed molecular studies and genotype-phenotype correlations. Patients: Thirty-five Japanese patients with POR deficiency participated in the study. Results: Mutation analysis revealed homozygosity for R457H in cases 1–14 (group A), compound heterozygosity for R457H and one apparently null mutation in cases 15–28 (group B), and other combinations of mutations in cases 29–35 (group C). In particular, FISH and RT-PCR sequencing analyses revealed an intragenic microdeletion in one apparent R457H homozygote, transcription failure of apparently normal alleles in three R457H heterozygotes, and nonsense mediated mRNA decay in two frameshift mutation-positive cases examined. Genotype-phenotype correlations indicated that skeletal features were definitely more severe, and adrenal dysfunction, 46,XY DSD, and pubertal failure were somewhat more severe in group B than group A, whereas 46,XX DSD and maternal virilization during pregnancy were similar between two groups. Notable findings also included the contrast between infrequent occurrence of 46,XY DSD and invariable occurrence of 46,XX DSD and pubertal growth pattern in group A mimicking that of aromatase deficiency. Conclusions: The results argue against the heterozygote manifestation and suggest that the residual POR activity reflected by the R457H dosage constitutes the underlying factor for clinical variability in some features but not other features, probably due to the simplicity and complexity of POR-dependent metabolic pathways relevant to each phenotype.

The 5α-reductase-2 encoded by the SRD5A2 gene plays a critical role in male sex differentiation by converting testosterone into 5α dihydrotestosterone in the peripheral target tissues. In this study, we examined the SRD5A2 gene in 81 Japanese patients with micropenis (age, 0–14 yr; median, 7 yr) whose stretched penile lengths were between −2.5 sd and −2.0 sd in 39 patients (age, 0–13 yr; median, 8 yr) and below −2.5 sd in 42 patients (age, 0–14 yr; median, 6 yr), together with 100 control males (50 boys and 50 fertile adult males). Mutation analysis was performed for exons 1–5 and their flanking introns by denaturing HPLC and direct sequencing, revealing Y26X/R227Q in an 11-yr-old boy with a penile length of −2.6 sd, G34R/R227Q in a 9-yr-old boy with a penile length of −3.6 sd, and R227Q/R227Q in a 3-yr-old boy with a penile length of −2.4 sd, together with heterozygous R227Q in a control boy and a fertile adult male. Polymorphism analysis was carried out for the most frequent V89L known to reduce the enzyme activity by approximately 30% in 78 patients, except for the three patients with SRD5A2 mutations, and in the 100 control males by direct sequencing, showing that allele and genotype frequencies were similar between 78 patients with micropenis below −2.0 sd or 40 patients with micropenis below −2.5 sd and the 100 control males, the 50 boys, or the 50 fertile adult males, with no statistically significant differences. The results suggest that, in Japanese patients, micropenis can be caused by SRD5A2 gene mutations, especially by R227Q which has been shown to retain approximately 3.2% of normal enzyme activity and appears relatively frequent in Asian populations, and that V89L polymorphism is unlikely to raise the susceptibility to the development of micropenis.

Context: Most patients with pediatric-onset primary adrenal insufficiency (PAI), such as 21-hydroxylase deficiency, can be diagnosed by measuring the urine or serum levels of steroid metabolites. However, the etiology is often difficult to determine in a subset of patients lacking characteristic biochemical findings. Objective: To assess the frequency of genetic defects in Japanese children with biochemically uncharacterized PAI and characterize the phenotypes of mutation-carrying patients. Methods: We enrolled 63 Japanese children (59 families) with biochemically uncharacterized PAI, and sequenced 12 PAI-associated genes. The pathogenicities of rare variants were assessed based on in silico analyses and structural modeling. We calculated the proportion of mutation-carrying patients according to demographic characteristics. Results: We identified genetic defects in 50 (85%) families: STAR in 19, NR0B1 in 18, SAMD9 in seven, AAAS in two, NNT in two, MC2R in one and CDKN1C in one. NR0B1 defects were identified in 78% of the male patients that received both glucocorticoid and mineralocorticoid replacement therapy and had normal male external genitalia. STAR defects were identified in 67% of female and 9% of male patients. Seven of the 19 patients with STAR defects developed PAI at age two or older, out of whom, five did not have mineralocorticoid deficiency. Conclusions: Molecular testing elucidated the etiologies of most biochemically uncharacterized PAI patients. Genetic defects such as NR0B1 defects are presumed based on phenotypes, while others with broad phenotypic variability, such as STAR defects, are difficult to diagnose. Molecular testing is a rational approach to diagnosis in biochemically uncharacterized PAI patients.

The steroidogenic acute regulatory protein (StAR) stimulates the regulated production of steroid hormones in the adrenal cortex and gonads by facilitating the delivery of cholesterol to the inner mitochondrial membrane. To explore key aspects of StAR function within bona fide steroidogenic cells, we used a transgenic mouse model to explore the function of StAR proteins in vivo. We first validated this transgenic bacterial artificial chromosome reconstitution system by targeting enhanced green fluorescent protein to steroidogenic cells of the adrenal cortex and gonads. Thereafter, we targeted expression of either wild-type StAR (WT-StAR) or a mutated StAR protein lacking the mitochondrial targeting signal (N47-StAR). In the context of mice homozygous for a StAR knockout allele (StAR^−/−), all StAR activity derived from the StAR transgenes, allowing us to examine the function of the proteins that they encode. The WT-StAR transgene consistently restored viability and steroidogenic function to StAR^−/− mice. Although the N47-StAR protein was reportedly active in transfected COS cells and mitochondrial reconstitution experiments, the N47-StAR transgene rescued viability in only 40% of StAR^−/− mice. Analysis of lipid deposits in the primary steroidogenic tissues revealed a hierarchy of StAR function provided by N47-StAR: florid lipid deposits were seen in the adrenal cortex and ovarian theca region, with milder deposits in the Leydig cells. Our results confirm the ability of StAR lacking its mitochondrial targeting signal to perform some essential functions in vivo but also demonstrate important functional defects that differ from in vitro studies obtained in nonsteroidogenic cells.