Activin controls skin morphogenesis and wound repair predominantly via stromal cells and in a concentration-dependent manner via keratinocytes

The transforming growth factor-beta family member activin is a potent regulator of skin morphogenesis and repair. Transgenic mice overexpressing activin in keratinocytes display epidermal hyper-thickening and dermal fibrosis in normal skin and enhanced granulation tissue formation after wounding. Mice overexpressing the secreted activin antagonist follistatin, however, have the opposite wound-healing phenotype. To determine whether activin affects skin morphogenesis and repair via activation of keratinocytes and/or stromal cells, we generated transgenic mice expressing a dominant-negative activin receptor IB mutant (dnActRIB) in keratinocytes. The architecture of adult skin was unaltered in these mice, but delays were observed in postnatal pelage hair follicle morphogenesis and in the first catagen-telogen transformation of hair follicles. Although dnActRIB-transgenic mice showed slightly delayed wound re-epithelialization after skin injury, the strong inhibition of granulation tissue formation seen in follistatin-transgenic mice was not observed. Therefore, although endogenous activin appeared to affect skin morphogenesis and repair predominantly via stromal cells, overexpressed activin strongly affected the epidermis. The epidermal phenotype of activin-overexpressing mice was partially rescued by breeding these animals with dnActRIB-transgenic mice. These results demonstrate that activin affects both stromal cells and keratinocytes in normal and wounded skin and that the effect on keratinocytes is dose-dependent in vivo.     

Transferability and Fine Mapping of Type 2 Diabetes Loci in African Americans: The Candidate Gene Association Resource Plus Study

Type 2 diabetes (T2D) disproportionally affects African Americans (AfA) but, to date, genetic variants identified from genome-wide association studies (GWAS) are primarily from European and Asian populations. We examined the single nucleotide polymorphism (SNP) and locus transferability of 40 reported T2D loci in six AfA GWAS consisting of 2,806 T2D case subjects with or without end-stage renal disease and 4,265 control subjects from the Candidate Gene Association Resource Plus Study. Our results revealed that seven index SNPs at the TCF7L2, KLF14, KCNQ1, ADCY5, CDKAL1, JAZF1, and GCKR loci were significantly associated with T2D (P < 0.05). The strongest association was observed at TCF7L2 rs7903146 (odds ratio [OR] 1.30; P = 6.86 × 10⁻⁸). Locus-wide analysis demonstrated significant associations (P_emp < 0.05) at regional best SNPs in the TCF7L2, KLF14, and HMGA2 loci as well as suggestive signals in KCNQ1 after correction for the effective number of SNPs at each locus. Of these loci, the regional best SNPs were in differential linkage disequilibrium (LD) with the index and adjacent SNPs. Our findings suggest that some loci discovered in prior reports affect T2D susceptibility in AfA with similar effect sizes. The reduced and differential LD pattern in AfA compared with European and Asian populations may facilitate fine mapping of causal variants at loci shared across populations.Type 2 diabetes (T2D) is a major public health problem affecting 25.8 million people in the U.S. (1). Marked racial differences in its prevalence have been observed, with African American (AfA) adults >40 years of age having nearly twofold higher prevalence than European Americans (27.1 and 15.5%, respectively) (2). In addition to socioeconomic and behavioral risk factors, genetic factors are likely contributors to T2D risk in AfA (3).Genome-wide association studies (GWAS) for T2D and related traits have successfully identified >50 loci with common genetic variants associated with T2D risk in primarily European-descent populations (4–14) and more recently in East and South Asians (15–21). The reported index single nucleotide polymorphisms (SNPs) at these loci have been replicated in multiple populations (22–24) but less successfully in AfA (25–27). Although differences in environment and lack of study power may partly account for the lack of transferability across ethnicities, differences in linkage disequilibrium (LD) patterns, effect sizes, and risk allele frequency also likely impact the replication of index SNPs. Although the long-range LD in European populations allows for the identification of T2D loci using less dense markers, causal variants are not distinguishable from other nearby SNPs in high LD. This issue prompts the need to examine T2D loci in other populations with different allelic and LD architecture, which may help fine mapping of the underlying functional variants (28).We performed a comprehensive evaluation of the LD region of T2D loci reported in European and Asian GWAS in a meta-analysis of six AfA GWAS. By testing the index and nearby SNPs, we evaluated the transferability of the previously reported loci for T2D association in AfA. We demonstrated that the reduced and differential LD structure in AfA facilitated fine mapping of regions potentially harboring causal variants at some T2D loci.     

On Efficient and Accurate Calculation of Significance P‐Values for Sequence Kernel Association Testing of Variant Set

The objective of this paper is to discuss and develop alternative computational methods to accurately and efficiently calculate significance P‐values for the commonly used sequence kernel association test (SKAT) and adaptive sum of SKAT and burden test (SKAT‐O) for variant set association. We show that the existing software can lead to either conservative or inflated type I errors. We develop alternative and efficient computational algorithms that quickly compute the SKAT P‐value and have well‐controlled type I errors. In addition, we derive an alternative and simplified formula for calculating the significance P‐value of SKAT‐O, which sheds light on the development of efficient and accurate numerical algorithms. We implement the proposed methods in the publicly available R package that can be readily used or adapted to large‐scale sequencing studies. Given that more and more large‐scale exome and whole genome sequencing or re‐sequencing studies are being conducted, the proposed methods are practically very important. We conduct extensive numerical studies to investigate the performance of the proposed methods. We further illustrate their usefulness with application to associations between rare exonic variants and fasting glucose levels in the Atherosclerosis Risk in Communities (ARIC) study.     

Estimation of Geographic Variation in Human Papillomavirus Vaccine Uptake in Men and Women: An Online Survey Using Facebook Recruitment

Background

Federally funded surveys of human papillomavirus (HPV) vaccine uptake are important for pinpointing geographically based health disparities. Although national and state level data are available, local (ie, county and postal code level) data are not due to small sample sizes, confidentiality concerns, and cost. Local level HPV vaccine uptake data may be feasible to obtain by targeting specific geographic areas through social media advertising and recruitment strategies, in combination with online surveys.

Objective

Our goal was to use Facebook-based recruitment and online surveys to estimate local variation in HPV vaccine uptake among young men and women in Minnesota.

Methods

From November 2012 to January 2013, men and women were recruited via a targeted Facebook advertisement campaign to complete an online survey about HPV vaccination practices. The Facebook advertisements were targeted to recruit men and women by location (25 mile radius of Minneapolis, Minnesota, United States), age (18-30 years), and language (English).

Results

Of the 2079 men and women who responded to the Facebook advertisements and visited the study website, 1003 (48.2%) enrolled in the study and completed the survey. The average advertising cost per completed survey was US $1.36. Among those who reported their postal code, 90.6% (881/972) of the participants lived within the previously defined geographic study area. Receipt of 1 dose or more of HPV vaccine was reported by 65.6% women (351/535), and 13.0% (45/347) of men. These results differ from previously reported Minnesota state level estimates (53.8% for young women and 20.8% for young men) and from national estimates (34.5% for women and 2.3% for men).

Conclusions

This study shows that recruiting a representative sample of young men and women based on county and postal code location to complete a survey on HPV vaccination uptake via the Internet is a cost-effective and feasible strategy. This study also highlights the need for local estimates to assess the variation in HPV vaccine uptake, as these estimates differ considerably from those obtained using survey data that are aggregated to the state or federal level.     

Suggestion for linkage of chromosome 1p35.2 and 3q28 to plasma adiponectin concentrations in the GOLDN Study

Background  

Adiponectin is inversely associated with obesity, insulin resistance, and atherosclerosis, but little is known about the genetic pathways that regulate the plasma level of this protein. To find novel genes that influence circulating levels of adiponectin, a genome-wide linkage scan was performed on plasma adiponectin concentrations before and after 3 weeks of treatment with fenofibrate (160 mg daily) in the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN) Study. We studied Caucasian individuals (n = 1121) from 190 families in Utah and Minnesota. Of these, 859 individuals from 175 families had both baseline and post-fenofibrate treatment measurements for adiponectin. Plasma adiponectin concentrations were measured with an ELISA assay. All participants were typed for microsatellite markers included in the Marshfield Mammalian Genotyping Service marker set 12, which includes 407 markers spaced at approximately 10 cM regions across the genome. Variance components analysis was used to estimate heritability and to perform genome-wide scans. Adiponectin was adjusted for age, sex, and field center. Additional models also included BMI adjustment.