Prenatal diagnosis of congenital lipoid adrenal hyperplasia

The hormonal control of parturition

Parturition is a complex physiological process that must occur in a reliable manner and at an appropriate gestation stage to ensure a healthy newborn and mother. To this end, hormones that affect the function of the gravid uterus, especially progesterone (P4), 17β-estradiol (E2), oxytocin (OT), and prostaglandins (PGs), play pivotal roles. P4 via the nuclear P4 receptor (PR) promotes uterine quiescence and for most of pregnancy exerts a dominant block to labor. Loss of the P4 block to parturition in association with a gain in prolabor actions of E2 are key transitions in the hormonal cascade leading to parturition. P4 withdrawal can occur through various mechanisms depending on species and physiological context. Parturition in most species involves inflammation within the uterine tissues and especially at the maternal-fetal interface. Local PGs and other inflammatory mediators may initiate parturition by inducing P4 withdrawal. Withdrawal of the P4 block is coordinated with increased E2 actions to enhance uterotonic signals mediated by OT and PGs to promote uterine contractions, cervix softening, and membrane rupture, i.e., labor. This review examines recent advances in research to understand the hormonal control of parturition, with focus on the roles of P4, E2, PGs, OT, inflammatory cytokines, and placental peptide hormones together with evolutionary biology of and implications for clinical management of human parturition.

Update and Review: Maternal Serum Screening

Maternal serum levels of alpha fetoprotein (AFP), human chorionic gonadotropin (hCG), and unconjugated estriol (uE3) can be used to screen pregnancies for neural tube defects, Down syndrome, Trisomy 18, and pregnancy complications. This article summarizes the most recent information regarding maternal serum screening, including genetic counseling issues.

Identification of novel mutations in STAR gene in patients with lipoid congenital adrenal hyperplasia: a first report from India

Lipoid congenital adrenal hyperplasia (LCAH), a rare disorder of steroid biosynthesis, is the most severe form of CAH. We report novel molecular findings of three unrelated infants with LCAH diagnosed at our center. A known missense mutation c.653C>T (p.A218V) and two novel mutations [premature termination c.441G>A (or p.W147X) and frameshift deletion c.del815G (or p.R272PfsX35)] were identified after complete sequencing of the STAR gene. Prenatal diagnosis was carried out for the family with mutation c.815delG by molecular testing wherein the fetus was found to be homozygous for the mutation. This is the first report of molecular diagnosis and prenatal testing for LCAH from India.

Prenatal diagnosis of congenital lipoid adrenal hyperplasia (CLAH) by molecular genetic testing in Korean siblings

Congenital lipoid adrenal hyperplasia (CLAH) is caused by mutations to the steroidogenic acute regulatory protein (StAR) gene associated with the inability to synthesize all adrenal and gonadal steroids. Inadequate treatment in an infant with this condition may result in sudden death from an adrenal crisis. We report a case in which CLAH developed in Korean siblings; the second child was prenatally diagnosed because the first child was affected and low maternal serum estriol was detected in a prenatal screening test. To our knowledge, this is the first prenatal diagnosis of the Q258X StAR mutation, which is the only consistent genetic cluster identified to date in Japanese and Korean populations.

Early steps in steroidogenesis: intracellular cholesterol trafficking

Steroid hormones are made from cholesterol, primarily derived from lipoproteins that enter cells via receptor-mediated endocytosis. In endo-lysosomes, cholesterol is released from cholesterol esters by lysosomal acid lipase (LAL; disordered in Wolman disease) and exported via Niemann-Pick type C (NPC) proteins (disordered in NPC disease). These diseases are characterized by accumulated cholesterol and cholesterol esters in most cell types. Mechanisms for trans-cytoplasmic cholesterol transport, membrane insertion, and retrieval from membranes are less clear. Cholesterol esters and "free" cholesterol are enzymatically interconverted in lipid droplets. Cholesterol transport to the cholesterol-poor outer mitochondrial membrane (OMM) appears to involve cholesterol transport proteins. Cytochrome P450scc (CYP11A1) then initiates steroidogenesis by converting cholesterol to pregnenolone on the inner mitochondrial membrane (IMM). Acute steroidogenic responses are regulated by cholesterol delivery from OMM to IMM, triggered by the steroidogenic acute regulatory protein (StAR). Chronic steroidogenic capacity is determined by CYP11A1 gene transcription. StAR mutations cause congenital lipoid adrenal hyperplasia, with absent steroidogenesis, potentially lethal salt loss, and 46,XY sex reversal. StAR mutations initially destroy most, but not all steroidogenesis; low levels of StAR-independent steroidogenesis are lost later due to cellular damage, explaining the clinical findings. Rare P450scc mutations cause a similar syndrome. This review addresses these early steps in steroid biosynthesis.

The active form of the steroidogenic acute regulatory protein, StAR, appears to be a molten globule

The steroidogenic acute regulatory protein (StAR) increases the movement of cholesterol from the outer to the inner membrane of adrenal and gonadal mitochondria, thus providing the substrate for steroid hormone biosynthesis. Deletion of 62 amino-terminal aa produces a cytoplasmic form of StAR (N-62 StAR) that lacks the mitochondrial leader sequence but retains full activity and appears to act at the outer mitochondrial membrane. At neutral pH the native state of bacterially expressed N-62 StAR protein displays cooperative unfolding under the influence of urea with DeltaGH2O = -4.1 kcal/mol, and it remains correctly folded down to pH 4. Limited proteolysis at different pHs shows that the biologically essential C-terminal region is accessible to solvent, and that the N-terminal domain is compact at pH 8 and partially unfolds below pH 4. Secondary structural analysis of CD curves suggests that the unfolding may coincide with an increase in alpha-helical character at pH 3.5. Fluorescence spectroscopy at pH 3-8 and at 0-6 M urea is consistent with two distinct domains, a compact N-terminal domain containing tryptophans 96 and 147 and a more solvent-accessible C-terminal domain containing tryptophans 241 and 250. These observations suggest that StAR forms a molten globule structure at pH 3.5-4.0. As the mitochondrial proton pump results in an electrochemical gradient, and as StAR must unfold during mitochondrial entry, StAR probably undergoes a similar conformational shift to an extended structure while interacting with the mitochondrial outer membrane, allowing this apparent molten globule form to act as an on/off switch for cholesterol entry into the mitochondria.