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 gain a better understanding of human disorders of puberty and reproduction. In collaboration with the Reproductive Endocrine Unit (REU) at the Massachusetts General Hospital (MGH), the Reproductive Physiology and Pathophysiology (RPP) Group at the National Institute of Environmental Health Sciences (NIEHS), and an ever growing network of international collaborations, 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 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 for, treatment of, and the long-term consequences of disorders of puberty and reproduction.
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. These 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 increase our understanding of the ontogeny of these disorders. Our phenotyping efforts found that uterine anomalies and Chiari type 1 malformations may represent novel, non-reproductive features of IGD, which is now being investigated in our genetic study (below) to determine whether there is a common molecular cause for these phenotypes. We 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 LB et al. N Engl J Med 1997;336:410) and reversal of the disorder after a period of treatment (Raivio T et al. N Engl J Med 2007;357:863). We recently reported that subjects with confirmed reversal, or recovery from HH with sustained endogenous LH pulsatility, are responsive to IV bolus infusions of kisspeptin, a neuropeptide known to be a key stimulus of GnRH release in the human. On the other hand, subjects who relapse from their recovery are not responsive to kisspeptin, whereas they do respond to GnRH, suggesting that pituitary responsiveness is intact. Thus, the acquisition and maintenance of kisspeptin responsiveness may play a role in reversal and, by extension, in pubertal development (Reference 1).
Neurocognitive effects of sex hormone deficiency at or before puberty
There is little existing evidence for the neurocognitive effects of delayed puberty. We performed neurocognitive testing and structural and functional MRI on subjects with IGD and compared 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, thus providing direct evidence in humans for the critical spatiotemporal role played by appropriately timed pubertal sex steroids during normal brain development. The final analysis of these data is being completed, with a manuscript in preparation.
Molecular basis of inherited reproductive disorders
Human and animal models have identified several genes responsible for IGD, but more than half the 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. The Molecular Genomics Core (NICHD) performed exome sequencing (ES) 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. In one of our larger families, we identified a novel candidate gene for Kallmann syndrome (KS), which is characterized by IHH and anosmia. All affected individuals in this family carry a heterozygous nonsense variant in a gene whose function has been indirectly associated in animal models with the neuronal migration defect affecting GnRH neurons and which is responsible for the KS phenotype. Functional validation of the role of this gene in IGD is planned.
In addition, through our collaboration with the REU at MGH, we also performed ES in several families with IGD and known uterine anomalies, and we have enrolled a cohort of individuals with delayed pubertal development and Chiari type 1 malformations, whose genomic DNA will soon be sent for ES, based on discoveries made through our phenotyping protocol. Analysis of these data has the potential to identify new non-reproductive features of IGD, as well as novel molecular pathways involved in the regulation of GnRH secretion and uterine or brain/skull development.
We are also investigating the role of genetic variants in 14 genes known to cause IGD in a subgroup of individuals with functional hypothalamic amenorrhea (HA), a hormonally similar condition that occurs in association with risk factors such as nutritional deprivation, exercise, or significant stress. 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, we would have further evidence that heterozygous variants in these genes may 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 candidate gene approaches have not been successful in identifying the molecular basis of this disorder. Thus, 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, as was recently shown with the identification of causative mutations in MKRN3, using ES (Abreu AP et al. N Engl J Med 2013; 368:2467). We have established collaborations with investigators both locally and internationally to increase recruitment of families with idiopathic CPP, and we are planning to perform ES analysis on this cohort in the coming months.
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 and 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, paradoxically, continuous administration of kisspeptin 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 previously funded through an NIH Bedside-to-Bench Award, we investigated 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 had been established, we planned 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. Unfortunately, as a result of insurmountable drug availability issues, this study was recently terminated.
Additional Funding
- 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)
- NICHD DIR Molecular Genomics Lab Sequencing Award, 2016: Novel Gene Discovery in Inherited Reproductive Disorders (ongoing)
Publications
- Lippincott MF, Chan YM, Delaney A, Rivera-Morales D, Butler JP, Seminara SB. Kisspeptin responsiveness signals emergence of reproductive endocrine activity: implications for human puberty. J Clin Endocrinol Metab 2016;101(8):3061-3069.
Collaborators
- Ravikumar Balasubramanian, MBBS, Massachusetts General Hospital, Boston, MA
- Jeffrey Baron, MD, Section on Growth and Development, 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
- James R. Iben, PhD, Molecular Genomics Core, NICHD, Bethesda, MD
- Youn Hee Jee, MD, Section on Growth and Development, NICHD, Bethesda, MD
- 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
Contact
For more information, email delaneya@mail.nih.gov.
