Biology subjects

Mika, K. M.

Publications and source records attributed to Mika, K. M..

3 recordsLinked to original sources

bioRxiv2018

An ancient fecundability-associated polymorphism creates a new GATA2 binding site in a distal enhancer of HLA-F

Variation in female reproductive traits such as fertility, fecundity, and fecundability are heritable in humans, but identifying and functionally characterizing genetic variants associated with these traits has been challenging. Here we explore the functional significance and evolutionary history of a G/A polymorphism of SNP rs2523393, which we have previously shown is an eQTL for the HLA-F gene and significantly associated with fecundability (time to pregnancy). We replicated the association between rs2523393 genotype and HLA-F expression using GTEx data and demonstrate that HLA-F is up-regulated in the endometrium during the window of implantation and by progesterone in decidual stromal cells. Next, we show that the rs2523393 A allele creates a new GATA2 binding site in a progesterone responsive distal enhancer that loops to the HLA-F promoter. Remarkably, we found that the A allele is derived in the human lineage, that G/A polymorphism arose before the divergence of modern and archaic humans, and is segregating at intermediate to high frequencies across human populations. Remarkably, the derived A is also has been identified in a GWAS as a risk allele for multiple sclerosis. These data suggests that the polymorphism is maintained by antagonistic pleiotropy and a reproduction-health tradeoff in human evolution.

genetics↗

bioRxiv2017

Energy demand and the context-dependent effects of genetic interactions

Genetic effects are often context dependent, with the same genotype differentially affecting phenotypes across environments, life stages, and sexes. We used an environmental manipulation designed to increase energy demand during development to investigate energy demand as a general physiological explanation for context-dependent effects of mutations, particularly for those mutations that affect metabolism. We found that increasing the photoperiod during which Drosophila larvae are active during development phenocopies a temperature-dependent developmental delay in a mitochondrial-nuclear genotype with disrupted metabolism. This result indicates that the context-dependent fitness effects of this genotype are not specific to the effects of temperature and may generally result from variation in energy demand. The effects of this genotype also differ across life stages and between the sexes. The mitochondrial-nuclear genetic interaction disrupts metabolic rate in growing larvae, but not in adults, and compromises female, but not male, reproductive fitness. These patterns are consistent with a model where context-dependent genotype-phenotype relationships may generally arise from differences in energy demand experienced by individuals across environments, life stages, and sexes.\n\nIMPACT SUMMARYGenetic effects on traits are often context dependent, such that a genotype that improves fitness under one context may have no effect or even a deleterious effect in another context. The external environment is a common context that affects the degree to which a genotype determines a phenotype, but the internal environment of an organism (e.g., its genetic background, sex or life stage) also provides an important context that may modify the phenotypic expression of a genotype. Here we combine new data on the phenotypic effects of a well-characterized genetic interaction between the mitochondrial and nuclear genomes of the fruit fly Drosophila with prior observations to support a model of energy demand as a general explanation for context-dependent genetic effects, particularly for mutations that affect metabolism. We show that the magnitude of fitness effects of this genetic interaction correlates positively with the degree of energy demand among developmental treatments that accelerate growth rate, across developmental stages that differ in the cost of growth, and between sexes with potentially different costs of reproduction. These internal and external contexts create variable demands on energy metabolism that will impact the efficacy of natural selection acting on metabolic mutations in populations.

evolutionary biology↗

bioRxiv2017

Accumulation And Functional Architecture Of Deleterious Genetic Variants During The Extinction Of Wrangel Island Mammoths

Woolly mammoths were among the most abundant cold adapted species during the Pleistocene. Their once large populations went extinct in two waves, an end-Pleistocene extinction of continental populations followed by the mid-Holocene extinction of relict populations on St. Paul Island ~5,600 years ago and Wrangel Island ~4,000 years ago. Wrangel Island mammoths experienced an episode of rapid demographic decline coincident with their isolation, leading to a small population, reduced genetic diversity, and the fixation of putatively deleterious alleles, but the functional consequences of these processes are unclear. Here we show that the Wrangel Island mammoth accumulated many putative deleterious mutations that are predicted to cause diverse behavioral and developmental defects. Resurrection and functional characterization of Wrangel Island mammoth genes carrying these substitutions identified both loss and gain of function mutations in genes associated with developmental defects (HYLS1), oligozoospermia and reduced male fertility (NKD1), diabetes (NEUROG3), and the ability to detect floral scents (OR5A1). These results suggest that Wrangel Island mammoths may have suffered adverse consequences from their reduced population sizes and isolation.

genetics↗