Recent advances in the study of genes involved in non-syndromic premature ovarian failure

Immunology of Addison's disease and premature ovarian failure

Autoimmune Addison's disease and autoimmune ovarian insufficiency are caused by selective targeting by T and B lymphocytes to the steroidogenic apparatus in these organs. Autoantibodies toward 21-hydroxylase are a clinically useful marker for autoimmune Addison's disease. Autoantibodies to 21-hydroxylase are found in premature ovarian insufficiency, but others also can be present, notably antibodies against side-chain cleavage enzyme. The autoimmune response primarily targets the theca cells, yielding elevated concentrations of inhibin, which is emerging as a useful diagnostic marker for autoimmune etiology of ovarian insufficiency. Little is known about its immunogenetics, but in contrast to Addison's disease, several experimental models of autoimmune premature ovarian insufficiency are available for study.

Gene expression analysis of human fetal ovarian primordial follicle formation

CONTEXT

Primordial follicle formation dictates the maximal potential female reproductive capacity and establishes the ovarian reserve. Currently, little is known about this process in the human.

OBJECTIVE

The aim of the study was to identify genes associated with the onset of human fetal primordial follicle formation in morphologically normal human fetuses.

DESIGN

We conducted an observational study of the female fetal gonad, comparing gene expression before and during primordial follicle formation.

SETTING

The study was conducted at the Universities of Aberdeen, Glasgow, and Nottingham.

PATIENTS/PARTICIPANTS

Ovaries were collected from 51 morphologically normal human female fetuses of women undergoing elective termination of normal second trimester pregnancies.

MAIN OUTCOME MEASURES

We performed fetal ovarian transcript expression by Affymetrix array and quantitative RT-PCR and gene product expression and localization by Western blot and immunohistochemistry.

RESULTS

Five transcripts were down-regulated and 61 were up-regulated in ovaries from older fetuses (18-20 wk) in which primordial follicle formation had started compared with younger (15-16 wk) fetuses in which no primordial follicles were observed. The altered genes contribute to major functions, including gene expression, tissue morphology, and apoptosis, that are essential for ovarian development. NALP5, the most highly regulated transcript, is an oocyte-specific maternal effect gene that is regulated downstream of FIGLA.

CONCLUSIONS

NALP5 probably plays a key role in the onset of human primordial follicle formation and thus the establishment of ovarian reserve in women.

Mutations in NR5A1 associated with ovarian insufficiency

BACKGROUND

The genetic causes of nonsyndromic ovarian insufficiency are largely unknown. A nuclear receptor, NR5A1 (also called steroidogenic factor 1), is a key transcriptional regulator of genes involved in the hypothalamic-pituitary-steroidogenic axis. Mutation of NR5A1 causes 46,XY disorders of sex development, with or without adrenal failure, but growing experimental evidence from studies in mice suggests a key role for this factor in ovarian development and function as well.

METHODS

To test the hypothesis that mutations in NR5A1 cause disorders of ovarian development and function, we sequenced NR5A1 in four families with histories of both 46,XY disorders of sex development and 46,XX primary ovarian insufficiency and in 25 subjects with sporadic ovarian insufficiency. None of the affected subjects had clinical signs of adrenal insufficiency.

RESULTS

Members of each of the four families and 2 of the 25 subjects with isolated ovarian insufficiency carried mutations in the NR5A1 gene. In-frame deletions and frameshift and missense mutations were detected. Functional studies indicated that these mutations substantially impaired NR5A1 transactivational activity. Mutations were associated with a range of ovarian anomalies, including 46,XX gonadal dysgenesis and 46,XX primary ovarian insufficiency. We did not observe these mutations in more than 700 control alleles.

CONCLUSIONS

NR5A1 mutations are associated with 46,XX primary ovarian insufficiency and 46,XY disorders of sex development.