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John C Achermann

Publications and source records attributed to John C Achermann.

24 records · Page 2Linked to original sources
PubMed2003

Battle of the sexes: new insights into genetic pathways of gonadal development.

Sex determination is governed by a series of genetic switches that influence cell fate and differentiation during critical periods of gonadal development. Remarkably, the primordial fetal gonad is bipotential. Therefore, gonadal development provides an excellent opportunity to identify genes involved in differential organogenesis. The identification of the testis-determining gene, SRY (Sex-reversed on the Y), was a pivotal first step towards unraveling this genetic pathway. It is now clear that numerous other genes, in addition to SRY, are necessary for normal testis development. For example, human mutations in a variety of genes (SOX9, WT1, SF1) impair testis development. Murine models provide evidence for additional genes (Lhx9, Emx2, M33, Dmrt, Fgf9). This lecture will highlight insights gleaned from human mutations in the nuclear receptors, SF1 (Steroidogenic Factor1) (NR5A1) and DAX1 (Dosage-sensitive sex reversal, Adrenal hypoplasia congenita, X chromosome) (NR0B1). These studies reveal the exquisite sensitivity of SF1-dependent developmental pathways to gene dosage and function in humans.

Adrenal Glands↗
PubMed2002

The role of SF1 in adrenal and reproductive function: insight from naturally occurring mutations in humans.

Steroidogenic factor 1 is a monomeric orphan nuclear receptor and one of several hundreds of transcription factors encoded in the human genome. It regulates the transcription of many genes involved in gonadal development, sexual differentiation, steroidogenesis and reproduction. Recently, mutations in the gene encoding SF1 have been identified in several patients with primary adrenal failure and 46,XY sex-reversal. Interpreting the consequences of these mutations provides further understanding of transcription factor haploinsufficiency in human genetic disease as well as the exquisite sensitivity of humans to gene-dosage effects during adrenal and gonadal development.

Adrenal Gland Diseases↗
PubMed2002

Progressive onset of adrenal insufficiency and hypogonadism of pituitary origin caused by a complex genetic rearrangement within DAX-1.

DAX-1 [dosage-sensitive sex reversal, adrenal hypoplasia congenital (AHC) critical region on the X chromosome, gene 1] is a transcription factor expressed in the adrenal gland and at all levels of the gonadotrope axis. Inactivating mutations of DAX1 result in the X-linked form of AHC with associated hypogonadotropic hypogonadism. AHC usually reveals itself as adrenal failure in early infancy, although a wide range of phenotypic expression has been reported. We describe a patient who was diagnosed with adrenal failure at 6 wk of age, but who experienced recovery of adrenal function of several months' duration later in infancy. He subsequently failed to undergo puberty because of hypogonadotropic hypogonadism of pituitary origin, and he was also diagnosed with schizophrenia in early adulthood. Molecular genetic analyses revealed a complex rearrangement in DAX1, including a 2.2-kb deletion spanning the entire second exon and a small 27-bp insertion. The putative protein encoded by this mutated gene is 429 amino acids long. The initial 389 residues probably correspond to the wild-type DAX-1 sequence, whereas the last 40 amino acids are presumably completely unrelated, being transcribed from the intronic sequence adjacent to exon 1. In vitro functional analyses confirm the absence of repressor activity exerted by such mutant protein. These studies expand the genotypic and phenotypic spectrum of DAX-1 insufficiency in humans.

Adolescent↗
PubMed2002

Hypogonadotropic hypogonadism as a presenting feature of late-onset X-linked adrenal hypoplasia congenita.

Mutations in the orphan nuclear receptor DAX-1 cause X-linked adrenal hypoplasia congenita. Affected boys usually present with primary adrenal failure in early infancy or childhood. Impaired sexual development because of hypogonadotropic hypogonadism becomes apparent at the time of puberty. We report adult-onset adrenal hypoplasia congenita in a patient who presented with hypogonadism at 28 yr of age. Although he had no clinical evidence of adrenal dysfunction, compensated primary adrenal failure was diagnosed by biochemical testing. Semen analysis showed azoospermia, and he did not achieve fertility after 8 months of treatment with gonadotropins. A novel Y380D DAX-1 missense mutation, which causes partial loss of function in transient gene expression assays, was found in this patient. This case demonstrates that partial loss-of-function mutations in DAX1 can present with hypogonadotropic hypogonadism and covert adrenal failure in adulthood. Further, an important role for DAX-1 in spermatogenesis in humans is confirmed, supporting findings in the Dax1 (Ahch) knockout mouse.

Adrenal Glands↗
PubMed2002

Gonadal determination and adrenal development are regulated by the orphan nuclear receptor steroidogenic factor-1, in a dose-dependent manner.

The orphan nuclear receptor steroidogenic factor-1 (SF-1, NR5A1) regulates the transcription of multiple genes involved in steroidogenesis, reproduction, and male sexual differentiation. A heterozygous loss-of-function SF-1 mutation (G35E) has been described in a patient with adrenal failure and complete 46XY sex-reversal, indicating that haploinsufficiency of this factor is sufficient to cause a severe clinical phenotype. This mutation in the P-box region of the DNA-binding domain markedly impairs SF-1 binding to most response elements. In an infant with a similar clinical phenotype, we identified an SF-1 mutation (R92Q) in a highly conserved residue of the A-box, a region that functions as a secondary DNA-binding domain. Strikingly, the affected infant was homozygous for the R92Q mutation, but three relatives (parents, sister) were phenotypically normal despite being heterozygous for the mutation. In functional assays, the R92Q mutant exhibited partial loss of DNA binding and transcriptional activity when compared with the G35E P-box change, consistent with its phenotypic expression only when transmitted as a homozygous trait. Taken together, these two naturally-occurring SF-1 mutations reveal the relative functional importance of the P-box and A-box regions for monomeric binding by nuclear receptors. In addition, these patients reveal the exquisite sensitivity of SF-1-dependent developmental pathways to gene dosage and function in humans.

Adrenal Glands↗