Regulation of Pubertal Onset and Reproductive Development
- Angela Delaney, MD, Head, Unit on Genetics of Puberty and Reproduction
- Rebecca Hicks, BA, Postbaccalaureate Intramural Research Training Award Fellow
- Alessandro Albano, BS, Postbaccalaureate Intramural Research Training Award Fellow
- Kyle R. Brunner, Special Volunteer
We are interested in identifying the initiating factors for pubertal onset in children. Our long-term goal is to define the developmental physiology of pubertal development, in order to increase our understanding of human disorders of puberty and reproduction. In collaboration with the Reproductive Endocrine Unit (REU) at the Massachusetts General Hospital (MGH), we are conducting translational research on the neuroendocrine and genetic control of gonadotropin-releasing hormone (GnRH) secretion and its regulation of gonadotropin secretion and gonadal physiology. We use molecular, cellular, and biochemical techniques, as well as comprehensive clinical phenotyping of human subjects to identify and characterize biological pathways that may contribute to the reactivation of GnRH secretion at puberty and to explore diagnostic techniques and treatment of disorders of puberty and reproduction.
The role of gonadotropin pulsations in the regulation of puberty and fertility
At one extreme of pubertal development, deficiency of GnRH results in a spectrum of rare clinical disorders of isolated GnRH deficiency (IGD), also known as idiopathic hypogonadotropic hypogonadism (IHH), which presents with delayed, incomplete, or absent sexual maturation. Defining the physiology of GnRH secretion is critical to understanding the clinical heterogeneity of IGD, particularly in light of emerging gene discoveries that aim to elucidate genotype-phenotype correlations. Non-reproductive phenotypic features have been identified in some individuals, including anosmia, auditory defects, and skeletal, neurological, and renal anomalies. The additional features may be the key to determining the developmental function of genes implicated in this spectrum of disorders.
Our clinical protocol, which is a multicenter study in collaboration with the REU at MGH, identified a broad range of luteinizing hormone (LH) pulsatility patterns and other features, which are being investigated in the context of genetic variants, where identified, in order to deepen our understanding of the ontogeny of these disorders. Our phenotyping efforts established that uterine anomalies may represent a novel non-reproductive feature of IGD, which is now being investigated in our genetic study (see below) to determine whether there is a common molecular cause for these phenotypes. We have also initiated a pilot study to determine the prevalence of psychiatric disorders and symptoms of negative emotional states in our cohort, compared with healthy controls, in order to determine whether there are previously unidentified psychological features in need of further investigation.
As a result of the phenotyping efforts pioneered by our collaborators at MGH, several rare phenotypic categories have been described in men with IGD, including adult-onset IHH (Nachtigall et al., N Engl J Med 1997;336:410) and reversal of the disorder after a period of treatment (Raivio et al., N Engl J Med 2007;357:863). However, the frequency of these phenotypes in women, in whom the disorder is five times less common, is unknown. Phenotypic characterization of females is further complicated by the possibility that they may be experiencing functional hypothalamic amenorrhea (HA), a hormonally similar condition that occurs in association with risk factors such as nutritional deprivation, exercise, or significant stress. We are working to characterize these phenotypic sub-categories in our cohort of females, in combination with our genetic analysis below, in order to provide insight into the phenotypic spectrum of GnRH–deficient disorders in women.
Neurocognitive effects of sex hormone deficiency at or before puberty
There is little evidence for the neurocognitive effects of delayed puberty. We therefore performed neurocognitive testing and structural and functional MRI on subjects with IGD, comparing them with healthy controls matched for age, sex, and race. Accounting for gender, our preliminary findings suggested that, in both sexes, pubertal sex steroid deficiency contributes to persistent structural and functional brain differences as well as to neurocognitive deficits, primarily involving spatial ability and recognition memory, providing direct evidence in humans of the critical spatiotemporal role played by appropriately timed pubertal sex steroids during normal brain development. Final analysis of the preliminary cohort in this study is under way.
The molecular basis of inherited reproductive disorders
Human and animal models have identified several genes responsible for IGD, but more than half of patients with clinical evidence of the disorder do not have a detectable mutation. In addition, there is significant clinical heterogeneity among affected individuals, including members of the same family harboring the same mutations, which is often explained by oligo-digenic inheritance patterns. Whole-exome sequencing (WES) was performed in the Molecular Genomics Lab (NICHD) on 28 probands participating in our genetic research protocol, including several extended families, to identify novel genes responsible for IGD. Data analysis is under way, and our findings are likely to yield important insights into additional pathways involved in the regulation of GnRH secretion. We also performed WES in several families with IGD and known uterine anomalies, based on our discovery that several patients have this phenotypic combination. Analysis of these data has the potential to identify a new non-reproductive feature of IGD, as well as a novel molecular pathway involved in the regulation of GnRH secretion and uterine development.
We have also been investigating genetic variants in 14 genes known to cause IGD in a subgroup of individuals with functional GnRH deficiency, resulting from HA, as described above. We aim to determine whether variants in the IGD genes are over-represented in individuals with HA, compared with the general population. If the data support our hypothesis, this would provide further evidence that heterozygous variants in these genes confer an increased susceptibility to developing HA in the setting of physiologic stressors, such as nutritional deficiency, extreme exercise, or psychological stress.
At the other extreme of pubertal development are patients with premature reactivation of hypothalamic GnRH secretion, resulting in idiopathic central precocious puberty (CPP). There is evidence that familial cases account for anywhere from 20–45% of CPP, with most studies describing autosomal dominant inheritance patterns. Far less is known about the molecular basis of CPP, and it was only recently that convincing evidence for a causative mutation was identified, using WES, in the MKRN3 gene (Abreu AP et al., N Engl J Med 2013;368:2467). Candidate gene approaches have not been successful in identifying the molecular basis of this disorder, and an unbiased approach to gene discovery seems more likely to achieve the goal of identifying novel candidate genes responsible for premature GnRH secretion in CPP. We are now actively recruiting familial cases of idiopathic CPP to undergo WES analysis. We have established collaborations with investigators both locally and internationally to increase enrollment, and we anticipate performing WES analysis on this cohort in the coming year.
Examining the genetic characteristics of subjects with pubertal disorders will reveal insights into the mechanisms underlying the reawakening of the hypothalamic-pituitary-gonadal axis at puberty. This will provide opportunities for new diagnostic capabilities and therapeutic interventions for disorders of puberty and reproduction.
Blockade of kisspeptin signaling in women
The neuropeptide hormone kisspeptin potently stimulates secretion of GnRH. While single doses of kisspeptin stimulate the reproductive endocrine axis, animal models suggest that continuous administration of kisspeptin paradoxically suppresses the reproductive endocrine axis temporarily through desensitization of the kisspeptin receptor. By administering 24-hour infusions of kisspeptin to healthy women and to patients with reproductive disorders, we hope to learn more about the role of kisspeptin both in normal physiology and in pathological conditions, such as polycystic ovary syndrome (PCOS), a common condition characterized by ovulatory dysfunction and hyperandrogenism. Among other disturbances of hormonal regulation, patients with PCOS have high-amplitude, high-frequency LH pulses, which may contribute to the oligo-anovulation characteristic of this disorder.
In collaboration with Stephanie Seminara, and funded through an NIH Bedside-to-Bench Award, we are investigating healthy postmenopausal women to determine the safety of continuous kisspeptin administration in women and the proper dose and conditions required to achieve desensitization of the kisspeptin receptor. Once these conditions have been established, we plan to administer the peptide to women with PCOS to determine whether abnormal kisspeptin signaling is involved in these disturbed endocrine dynamics, as greater understanding of how kisspeptin modulates GnRH secretion in this condition could lead to novel therapeutic interventions for this patient population.
- NICHD DIR Molecular Genomics Lab Sequencing Award, 2014: Novel Gene Discovery in Inherited Reproductive Disorders (ongoing)
- NICHD DIR Molecular Genomics Lab Sequencing Award, 2015: Novel Gene Discovery in Inherited Reproductive Disorders (ongoing)
- Delaney A, Padmanabhan V, Rezvani G, Chen W, Forcinito P, Cheung CS, Baron J, Lui JC. Evolutionary conservation and modulation of a juvenile growth-regulating genetic program. J Mol Endocrinol 2014 52(3):269-277.
- Ravikumar Balasubramanian, MBBS, Massachusetts General Hospital, Boston, MA
- Jeffrey Baron, MD, Program on Developmental Endocrinology and Genetics, NICHD, Bethesda, MD
- Jonathan Blumenthal, MA, Child Psychiatry Branch, NIMH, Bethesda, MD
- Raja Brauner, MD, Université Paris Descartes and Fondation Ophtalmologique Adolphe de Rothschild, Paris, France
- Yee-Ming Chan, MD, PhD, Massachusetts General Hospital, Boston, MA
- William F. Crowley, Jr., MD, Massachusetts General Hospital, Boston, MA
- Jay N. Giedd, MD, Child Psychiatry Branch, NIMH, Bethesda, MD
- Janet E. Hall, MD, Massachusetts General Hospital, Boston, MA, and Clinical Research Unit, NIEHS, Research Triangle Park, NC
- Francois Lalonde, PhD, Child Psychiatry Branch, NIMH, Bethesda, MD
- Margaret F. Lippincott, MD, Massachusetts General Hospital, Boston, MA
- Kenneth McElreavey, PhD, Institut Pasteur, Paris, France
- Veronica Mericq, MD, University of Chile, Santiago, Chile
- Paulina Merino, MD, University of Chile, Santiago, Chile
- Lacey Plummer, MS, Massachusetts General Hospital, Boston, MA
- Richard Quinton, MB, BChir, MD, FRCP, Newcastle University, Newcastle-upon-Tyne, United Kingdom
- Stephanie B. Seminara, MD, Massachusetts General Hospital, Boston, MA
- Natalie D. Shaw, MD, MMSc, Massachusetts General Hospital, Boston, MA
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