Luca Persani

Hypergonadotropic Ovarian Failure Associated with an Inherited Mutation of Human Bone Morphogenetic Protein-15 (BMP15) Gene

Hypergonadotropic ovarian failure is a common cause of female infertility. It is a heterogeneous disorder that, in the most severe forms, is a result of ovarian dysgenesis (OD). Most OD cases are associated with major X-chromosome abnormalities, but the pathogenesis of this disorder is still largely undefined in patients with a normal karyotype. Animal models showed the important role in female reproduction played by the product of a gene located at Xp11.2 in humans (BMP15). BMP15 is an oocyte-specific growth/differentiation factor that stimulates folliculogenesis and granulosa cell (GC) growth. We report two sisters with a normal karyotype who are affected with hypergonadotropic ovarian failure due to OD. The familial presentation suggested a genetic origin, and candidate genes were screened for mutations. A heterozygous nonconservative substitution in the pro region of BMP15 (Y235C) was identified in both sisters but not in 210 control alleles. This mutation was inherited from the father. Mutant BMP15 appears to be processed abnormally, is associated with reduced GC growth, and antagonizes the stimulatory activity of wild-type protein on GC proliferation. In conclusion, the first natural mutation in human BMP15 is associated with familial OD, indicating that the action of BMP15 is required for the progression of human folliculogenesis. This condition represents an exceptional example of X-linked human disease exclusively affecting heterozygous females who inherited the genetic alteration from the unaffected father. BMP15 defects are involved in the pathogenesis of hypergonadotropic ovarian failure in humans.

Persistent cAMP-Signals Triggered by Internalized G-Protein–Coupled Receptors

Real-time monitoring of G-protein-coupled receptor (GPCR) signaling in native cells suggests that the receptor for thyroid stimulating hormone remains active after internalization, challenging the current model for GPCR signaling.

Signaling by internalized G-protein-coupled receptors

G-protein-coupled receptors (GPCRs) are cell surface receptors and are generally assumed to signal to second messengers such as cyclic AMP (cAMP) exclusively from the plasma membrane. However, recent studies indicate that GPCRs can continue signaling to cAMP after internalization together with their agonists. Signaling from inside the cell is persistent and appears to trigger specific downstream effects. Here, we will review these recent data, which form the basis for a novel concept of intracellular GPCR signaling and suggest new and intriguing scenarios for the functions of GPCRs in the endocytic compartment. We propose that current models of GPCR signaling should be revised to accommodate the ability of receptors to change their signaling properties depending on their subcellular localization.

Premature ovarian failure

Premature ovarian failure (POF) is a primary ovarian defect characterized by absent menarche (primary amenorrhea) or premature depletion of ovarian follicles before the age of 40 years (secondary amenorrhea). It is a heterogeneous disorder affecting approximately 1% of women <40 years, 1:10,000 women by age 20 and 1:1,000 women by age 30. The most severe forms present with absent pubertal development and primary amenorrhea (50% of these cases due to ovarian dysgenesis), whereas forms with post-pubertal onset are characterized by disappearance of menstrual cycles (secondary amenorrhea) associated with premature follicular depletion. As in the case of physiological menopause, POF presents by typical manifestations of climacterium: infertility associated with palpitations, heat intolerance, flushes, anxiety, depression, fatigue. POF is biochemically characterized by low levels of gonadal hormones (estrogens and inhibins) and high levels of gonadotropins (LH and FSH) (hypergonadotropic amenorrhea). Beyond infertility, hormone defects may cause severe neurological, metabolic or cardiovascular consequences and lead to the early onset of osteoporosis. Heterogeneity of POF is also reflected by the variety of possible causes, including autoimmunity, toxics, drugs, as well as genetic defects. POF has a strong genetic component. X chromosome abnormalities (e.g. Turner syndrome) represent the major cause of primary amenorrhea associated with ovarian dysgenesis. Despite the description of several candidate genes, the cause of POF remains undetermined in the vast majority of the cases. Management includes substitution of the hormone defect by estrogen/progestin preparations. The only solution presently available for the fertility defect in women with absent follicular reserve is ovum donation.

X Chromosome Monosomy: A Common Mechanism for Autoimmune Diseases

The majority of human autoimmune diseases are characterized by female predominance. Although sex hormone influences have been suggested to explain this phenomenon, the mechanism remains unclear. In contrast to the role of hormones, it has been suggested, based on pilot data in primary biliary cirrhosis, that there is an elevation of monosomy X in autoimmune disease. Using peripheral white blood cells from women with systemic sclerosis (SSc), autoimmune thyroid disease (AITD), or healthy age-matched control women, we studied the presence of monosomy X rates using fluorescence in situ hybridization. We also performed dual-color fluorescence in situ hybridization analysis with a chromosome Y α-satellite probe to determine the presence of the Y chromosome in the monosomic cells. In subsets of patients and controls, we determined X monosomy rates in white blood cell subpopulations. The rates of monosomy X increased with age in all three populations. However, the rate of monosomy X was significantly higher in patients with SSc and AITD when compared with healthy women (6.2 ± 0.3% and 4.3 ± 0.3%, respectively, vs 2.9 ± 0.2% in healthy women, p < 0.0001 in both comparisons). Importantly, X monosomy rate was more frequent in peripheral T and B lymphocytes than in the other blood cell populations, and there was no evidence for the presence of male fetal microchimerism. These data highlight the thesis that chromosome instability is common to women with SSc and AITD and that haploinsufficiency for X-linked genes may be a critical factor for the female predominance of autoimmune diseases.

Luteinizing Hormone Signaling in Preovulatory Follicles Involves Early Activation of the Epidermal Growth Factor Receptor Pathway

LH activates a cascade of signaling events that are propagated throughout the ovarian preovulatory follicle to promote ovulation of a mature egg. Critical to LH-induced ovulation is the induction of epidermal growth factor (EGF)-like growth factors and transactivation of EGF receptor (EGFR) signaling. Because the timing of this transactivation has not been well characterized, we investigated the dynamics of LH regulation of the EGF network in cultured follicles. Preovulatory follicles were cultured with or without recombinant LH and/or specific inhibitors. EGFR and MAPK phosphorylation were examined by immunoprecipitation and Western blot analyses. By semiquantitative RT-PCR, increases in amphiregulin and epiregulin mRNAs were detected 30 min after recombinant LH stimulation of follicles and were maximal after 2 h. LH-induced EGFR phosphorylation also increased after 30 min and reached a maximum at 2 h. EGFR activation precedes oocyte maturation and is cAMP dependent, because forskolin similarly activated EGFR. LH-induced EGFR phosphorylation was sensitive to AG1478, an EGFR kinase inhibitor, and to inhibitors of matrix metalloproteases GM6001 and TNFalpha protease inhibitor-1 (TAPI-1), suggesting the involvement of EGF-like growth factor shedding. LH- but not amphiregulin-induced oocyte maturation and EGFR phosphorylation were sensitive to protein synthesis inhibition. When granulosa cells were cultured with a combination of neutralizing antibodies against amphiregulin, epiregulin, and betacellulin, EGFR phosphorylation and MAPK activation were inhibited. In cultured follicles, LH-induced MAPK activation was partially inhibited by AG1478 and GM6001, indicating that this pathway is regulated in part by the EGF network but also involves additional pathways. Thus, complex mechanisms are involved in the rapid amplification and propagation of the LH signal within preovulatory follicles and include the early activation of the EGF network.

A 7-year experience with low blood TSH cutoff levels for neonatal screening reveals an unsuspected frequency of congenital hypothyroidism (CH)

Context  The guidelines of the National Academy of Clinical Biochemistry advocated the use of low bloodspot TSH (b‐TSH) threshold for newborn screening of congenital hypothyroidism (CH). The impact generated by the application of this indication is largely unknown.

Genes involved in human premature ovarian failure

Premature ovarian failure (POF) is an ovarian defect characterized by the premature depletion of ovarian follicles before the age of 40 years, representing one major cause of female infertility. POF relevance is continuously growing because women tend to conceive ever more frequently in their thirties and forties. POF can present very early with a pubertal defect. More frequently, it is the end stage of an occult process (primary ovarian insufficiency, POI) affecting ∼ 1-2% of under-40 women. POI is a heterogeneous disease caused by a variety of mechanisms. Though the underlying cause remains unexplained in the majority of cases, various data indicate that POI has a strong genetic component. These data include the existence of several causal genetic defects in humans, experimental and natural models, as well as the frequent familiarity. The variable expressivity of POI defect in women of the same family may indicate that, in addition to some monogenic forms, POI may frequently be considered as a multifactorial defect resulting from the contribution of several predisposing alleles. The X chromosome-linked defects play a major role among the presently known causal defects. Here, we review the principal X-linked and autosomal genes involved in syndromic and nonsyndromic forms of POI with the wish that this list will soon become upgraded because of the discovery of novel contributing mechanisms. A better understanding of POI pathogenesis will indeed allow the construction of tests able to predict the age of menopause in women at higher risk of POI.

Regulation of ovulation rate in mammals: contribution of sheep genetic models

Ovarian folliculogenesis in mammals from the constitution of primordial follicles up to ovulation is a reasonably well understood mechanism. Nevertheless, underlying mechanisms that determine the number of ovulating follicles were enigmatic until the identification of the fecundity genes affecting ovulation rate in sheep, bone morphogenetic protein-15 (BMP-15), growth and differentiation factor-9 (GDF-9) and BMP receptor-1B (BMPR-1B). In this review, we focus on the use of these sheep genetic models for understanding the role of the BMP system as an intra-ovarian regulator of follicular growth and maturation, and finally, ovulation rate.

A Meta-Analysis of Thyroid-Related Traits Reveals Novel Loci and Gender-Specific Differences in the Regulation of Thyroid Function

Thyroid hormone is essential for normal metabolism and development, and overt abnormalities in thyroid function lead to common endocrine disorders affecting approximately 10% of individuals over their life span. In addition, even mild alterations in thyroid function are associated with weight changes, atrial fibrillation, osteoporosis, and psychiatric disorders. To identify novel variants underlying thyroid function, we performed a large meta-analysis of genome-wide association studies for serum levels of the highly heritable thyroid function markers TSH and FT4, in up to 26,420 and 17,520 euthyroid subjects, respectively. Here we report 26 independent associations, including several novel loci for TSH (PDE10A, VEGFA, IGFBP5, NFIA, SOX9, PRDM11, FGF7, INSR, ABO, MIR1179, NRG1, MBIP, ITPK1, SASH1, GLIS3) and FT4 (LHX3, FOXE1, AADAT, NETO1/FBXO15, LPCAT2/CAPNS2). Notably, only limited overlap was detected between TSH and FT4 associated signals, in spite of the feedback regulation of their circulating levels by the hypothalamic-pituitary-thyroid axis. Five of the reported loci (PDE8B, PDE10A, MAF/LOC440389, NETO1/FBXO15, and LPCAT2/CAPNS2) show strong gender-specific differences, which offer clues for the known sexual dimorphism in thyroid function and related pathologies. Importantly, the TSH-associated loci contribute not only to variation within the normal range, but also to TSH values outside the reference range, suggesting that they may be involved in thyroid dysfunction. Overall, our findings explain, respectively, 5.64% and 2.30% of total TSH and FT4 trait variance, and they improve the current knowledge of the regulation of hypothalamic-pituitary-thyroid axis function and the consequences of genetic variation for hypo- or hyperthyroidism.