Large-scale meta-analysis highlights the hypothalamic–pituitary–gonadal axis in the genetic regulation of menstrual cycle length

The normal menstrual cycle requires a delicate interplay between the hypothalamus, pituitary and ovary. Therefore, its length is an important indicator of female reproductive health. Menstrual cycle length has been shown to be partially controlled by genetic factors, especially in the follicle-stimulating hormone beta-subunit (FSHB) locus. A genome-wide association study meta-analysis of menstrual cycle length in 44 871 women of European ancestry confirmed the previously observed association with the FSHB locus and identified four additional novel signals in, or near, the GNRH1, PGR, NR5A2 and INS-IGF2 genes. These findings not only confirm the role of the hypothalamic–pituitary–gonadal axis in the genetic regulation of menstrual cycle length but also highlight potential novel local regulatory mechanisms, such as those mediated by IGF2

Machine Learning based histology phenotyping to investigate the epidemiologic and genetic basis of adipocyte morphology and cardiometabolic traits

Genetic studies have recently highlighted the importance of fat distribution, as well as overall adiposity, in the pathogenesis of obesity-associated diseases. Using a large study (n = 1,288) from 4 independent cohorts, we aimed to investigate the relationship between mean adipocyte area and obesity-related traits, and identify genetic factors associated with adipocyte cell size. To perform the first large-scale study of automatic adipocyte phenotyping using both histological and genetic data, we developed a deep learning-based method, the Adipocyte U-Net, to rapidly derive mean adipocyte area estimates from histology images. We validate our method using three state-of-the-art approaches; CellProfiler, Adiposoft and floating adipocytes fractions, all run blindly on two external cohorts. We observe high concordance between our method and the state-of-the-art approaches (Adipocyte U-net vs. CellProfiler: R2visceral = 0.94, P < 2.2 × 10-16, R2subcutaneous = 0.91, P < 2.2 × 10-16), and faster run times (10,000 images: 6mins vs 3.5hrs). We applied the Adipocyte U-Net to 4 cohorts with histology, genetic, and phenotypic data (total N = 820). After meta-analysis, we found that mean adipocyte area positively correlated with body mass index (BMI) (Psubq = 8.13 × 10-69, βsubq = 0.45; Pvisc = 2.5 × 10-55, βvisc = 0.49; average R2 across cohorts = 0.49) and that adipocytes in subcutaneous depots are larger than their visceral counterparts (Pmeta = 9.8 × 10-7). Lastly, we performed the largest GWAS and subsequent meta-analysis of mean adipocyte area and intra-individual adipocyte variation (N = 820). Despite having twice the number of samples than any similar study, we found no genome-wide significant associations, suggesting that larger sample sizes and a homogenous collection of adipose tissue are likely needed to identify robust genetic associations.This article is freely available via Open Access. Click on the Publisher URL to access it via the publisher's site.C.A.G received a pump priming grant from Novo Nordisk to carry out this work. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.published version, accepted versio

Deciphering the function of obesity-associated regulatory elements within FTO

Genome-wide association studies have repeatedly shown that the strongest association with obesity arises from variants in the first intron of FTO. The intronic FTO variant rs1421085 is within an adipocyte-specific enhancer and that risk allele carriers have increased IRX3 and IRX5 expression in early adipogenesis (Claussnitzer et al., 2015). Additionally, the same human risk variant was linked to decreased AKTIP, RPGRIP1L and FTO expression in iPSC-derived neurons (Stratigopoulos et al., 2016). These data point towards several likely causal transcripts and tissues at the FTO locus and essentially, several likely mechanisms. Importantly, whether any of the high-risk variants at the FTO locus has any effect on the organismal level has not been addressed so far. The aim of my DPhil project was to use novel gene manipulation strategies in vivo to mechanistically dissect the Fto regulatory circuitry in mouse to pinpoint causal transcripts their effector tissues and to unravel their physiological role in body weight regulation . Using publicly available as well as my own genomic data (ATAC-seq) revealed that the intronic FTO regulatory element in human adipocytes is conserved in mouse pre-adipocytes. Manipulation of the corresponding motif in mouse (by deleting 82 nucleotides at the mouse orthologous region around rs1421085) resulted in depot- and sex-specific alteration of target genes Irx3 and Irx5 in pre-adipocytes. In addition to recapitulating many of the human findings in mouse, my results further unravelled a new level of regulatory complexity at the FTO/Fto locus. When these mutant mice were put on a high fat diet, I found a reduction on overall fat-mass that could be linked to altered mRNA levels of Irx3 and Irx5 in pre-adipocytes. Using a number of genetic techniques, I further showed that Irx3 regulates several processes during adipocyte development, amongst which is modulation of mitochondrial function. In summary, my findings provide new insight into how variants in FTO intron 1 affect adipocyte development and more specifically how IRX3 affects early adipocyte differentiation.</p

Deciphering the function of obesity-associated regulatory elements within FTO

Genome-wide association studies have repeatedly shown that the strongest association with obesity arises from variants in the first intron of FTO. The intronic FTO variant rs1421085 is within an adipocyte-specific enhancer and that risk allele carriers have increased IRX3 and IRX5 expression in early adipogenesis (Claussnitzer et al., 2015). Additionally, the same human risk variant was linked to decreased AKTIP, RPGRIP1L and FTO expression in iPSC-derived neurons (Stratigopoulos et al., 2016). These data point towards several likely causal transcripts and tissues at the FTO locus and essentially, several likely mechanisms. Importantly, whether any of the high-risk variants at the FTO locus has any effect on the organismal level has not been addressed so far. The aim of my DPhil project was to use novel gene manipulation strategies in vivo to mechanistically dissect the Fto regulatory circuitry in mouse to pinpoint causal transcripts their effector tissues and to unravel their physiological role in body weight regulation . Using publicly available as well as my own genomic data (ATAC-seq) revealed that the intronic FTO regulatory element in human adipocytes is conserved in mouse pre-adipocytes. Manipulation of the corresponding motif in mouse (by deleting 82 nucleotides at the mouse orthologous region around rs1421085) resulted in depot- and sex-specific alteration of target genes Irx3 and Irx5 in pre-adipocytes. In addition to recapitulating many of the human findings in mouse, my results further unravelled a new level of regulatory complexity at the FTO/Fto locus. When these mutant mice were put on a high fat diet, I found a reduction on overall fat-mass that could be linked to altered mRNA levels of Irx3 and Irx5 in pre-adipocytes. Using a number of genetic techniques, I further showed that Irx3 regulates several processes during adipocyte development, amongst which is modulation of mitochondrial function. In summary, my findings provide new insight into how variants in FTO intron 1 affect adipocyte development and more specifically how IRX3 affects early adipocyte differentiation.</p

Response to comment on “Evaluating the cardiovascular safety of sclerostin inhibition using evidence from meta-analysis of clinical trials and human genetics”

Triangulation of evidence from clinical trials and human genetics suggests a potential excess risk of cardiovascular disease events arising from therapeutic inhibition of sclerostin

A regulatory variant at 3q21.1 confers an increased pleiotropic risk for hyperglycemia and altered bone mineral density

Skeletal and glycemic traits have shared etiology, but the underlying genetic factors remain largely unknown. To identify genetic loci that may have pleiotropic effects, we studied Genome-wide association studies (GWASs) for bone mineral density and glycemic traits and identified a bivariate risk locus at 3q21. Using sequence and epigenetic modeling, we prioritized an adenylate cyclase 5 (ADCY5) intronic causal variant, rs56371916. This SNP changes the binding affinity of SREBP1 and leads to differential ADCY5 gene expression, altering the chromatin landscape from poised to repressed. These alterations result in bone- and type 2 diabetes-relevant cell-autonomous changes in lipid metabolism in osteoblasts and adipocytes. We validated our findings by directly manipulating the regulator SREBP1, the target gene ADCY5, and the variant rs56371916, which together imply a novel link between fatty acid oxidation and osteoblast differentiation. Our work, by systematic functional dissection of pleiotropic GWAS loci, represents a framework to uncover biological mechanisms affecting pleiotropic traits