The Genetics of Pubertal Growth and Timing

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http://urn.fi/URN:ISBN:978-951-51-0975-0
Title: The Genetics of Pubertal Growth and Timing
Author: Cousminer, Diana
Contributor: University of Helsinki, Faculty of Medicine, Hjelt Institute
Institute for Molecular Medicine Finland (FIMM)
Publisher: Helsingin yliopisto
Date: 2015-04-17
URI: http://urn.fi/URN:ISBN:978-951-51-0975-0
http://hdl.handle.net/10138/153863
Thesis level: Doctoral dissertation (article-based)
Abstract: Puberty is a highly variable developmental stage marked by the development of secondary sex characteristics and the attainment of reproductive maturity. Variation during childhood developmental phases correlates with altered disease risk in adulthood; variation in pubertal growth and timing, in particular, correlates with adult risk for type 2 diabetes, obesity, adverse cardiovascular heath, and hormone-dependent cancers. While normal variation in age at menarche (AAM) has recently been investigated in large-scale genome-wide association (GWA) studies, the genetic regulation of male puberty remains less understood. Moreover, extreme variation in pubertal timing is a common cause for referral to pediatric specialists, while the underlying genetic factors are largely unknown. This work aimed to identify both common and rare genetic variants influencing pubertal growth and timing in both sexes. Utilizing Finnish population-based samples with frequent height measurements across puberty, we ran GWA of growth during late puberty and uncovered an association for variants near LIN28B, the most robust menarche-associated locus. Investigation of the longitudinal effects of two partly-correlated markers, one tagging a pubertal timing effect and one tagging an effect on adult stature, revealed distinct sex-specific association patterns with height growth from birth until adulthood. Thus, the LIN28B locus tags an important developmental regulator of both growth and maturational development. We then expanded to include European-wide samples within the Early Growth Genetics (EGG) Consortium. Genetic mapping of three pubertal growth traits revealed 9 novel pubertal growth variants in addition to LIN28B, 5 of which also associated with pubertal timing, and one which associated with childhood and adult body mass index (BMI). Longitudinal investigation of these variants showed diverse patterns of association with height growth, some of which contradicted epidemiological correlations between rapid prepubertal growth, advanced puberty, and reduced final adult stature. Given the complex relationships between these traits, tracking individual unique effects across multiple periods of growth may help uncover the pathways linking childhood development with adult health outcomes. Also within the EGG Consortium, GWA meta-analysis of Tanner genital and breast staging data uncovered the first robust male puberty locus on chromosome 16 near MKL2, a locus which also associates with advanced menarche, decreased pubertal growth, and shorter adult stature. Furthermore, part of the genetic architecture underlying the onset of puberty is shared between males and females, evidenced by the high correlation between menarche-advancing alleles and earlier male genital development. However, while BMI-increasing alleles strongly correlate with advanced breast development in girls, our data shows that these variants play a more complex role in male puberty. Finally, we performed targeted sequencing of the pericentromeric region of chromosome 2 previously robustly linked with constitutional delay of growth and puberty (CDGP), an extreme delay in normal pubertal timing, in multiply affected Finnish families. Analysis of shared low-frequency variation in genes and regulatory regions of the best functional candidate genes revealed 6 protein-altering variants in a single gene, DNAH6, in 10 of the families. However, follow-up sequencing in an additional 135 Finnish CDGP cases failed to provide evidence for enrichment of DNAH6 mutations compared to a large, unique set of SISu Finnish population controls. DNAH6 is potentially an appropriate candidate gene that may be involved in the regulation of steroid hormone biosynthesis by the cytoskeleton. This study highlights the difficulties of detecting susceptibility variants under a linkage signal for complex traits. Taken together, these results advance our understanding of the genetics of pubertal timing and development in both sexes. However, more work is needed to understand how each genetic locus functions in the biology of puberty and childhood growth, and further study of the genetic loci highlighted in this work may help pinpoint the mechanisms that link the timing of this important developmental stage with adult health and risk for common diseases. Keywords: puberty, development, growth, genome-wide association studies (GWAS), targeted sequencing, constitutional delay of growth and puberty (CDGP)none
Subject: genetics
Rights: This publication is copyrighted. You may download, display and print it for Your own personal use. Commercial use is prohibited.


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