Biomedical subjects

Richard P Woychik

Publications and source records attributed to Richard P Woychik.

5 recordsLinked to original sources

PubMed2026

Disentangling Sex Differences in Sulfonylurea Drug Response With Genome-Wide Association Studies in Individuals With Type 2 Diabetes.

Sulfonylureas are a cornerstone of type 2 diabetes therapy despite interindividual variability in response. Despite well-documented sex-based differences, pharmacogenomic and genome-wide association studies (GWAS) have largely overlooked sex as a biological variable. We conducted the first sex-stratified GWAS of hemoglobin A1c (HbA1c) response to sulfonylureas in Action to Control Cardiovascular Risk in Diabetes (ACCORD) clinical trial participants (N = 871). Variants meeting genome-wide (P < 5.0 × 10-8) and suggestive (P < 5.0 × 10-6) significance were assessed for replication in the Pharmacogenomics of Metformin (PMET1) cohort. Replicated variants were further analyzed in the Study to Understand the Genetics of the Acute Response to Metformin and Glipizide in Humans (SUGAR-MGH) cohort to assess acute insulin and glucose responses to a single glipizide dose. Genome-wide significant loci with sex-specific effects were identified: KAZN, KIF2B, SLC39A10, and SPINK5 (combined-sex); CRACR2A, KCNK2, and TENM2 (male-only); and NACPH2 (female-only). Two suggestive variants in the TMEM64/NECAB1 locus, associated with reduced HbA1c response to sulfonylureas in the male-only ACCORD analysis, were directly replicated in the PMET1 male-only cohort. In SUGAR-MGH, one replicated variant (rs6471250-C) was significantly associated with reduced peak insulin in males (P = 0.035) but not females (P = 0.40), demonstrating sex-specific functional effects. This study identified statistically supported and biologically plausible loci with prior evidence linking nearby genes to pathways relevant to sulfonylurea action, including insulin secretion, insulin regulation/sensitivity, calcium signaling, potassium-channel biology, and glucose transport. The findings highlight sex-specific differences in sulfonylurea response, providing mechanistic insights and underscoring the importance of sex-specific precision medicine. Identification of genetic variants influencing sex-specific response could inform dosing to optimize sulfonylureas.

Humans↗

PubMed2004

Liver-specific expression of the agouti gene in transgenic mice promotes liver carcinogenesis in the absence of obesity and diabetes.

BACKGROUND: The agouti protein is a paracrine factor that is normally present in the skin of many species of mammals. Agouti regulates the switch between black and yellow hair pigmentation by signalling through the melanocortin 1 receptor (Mc1r) on melanocytes. Lethal yellow (Ay) and viable yellow (Avy) are dominant regulatory mutations in the mouse agouti gene that cause the wild-type protein to be produced at abnormally high levels throughout the body. Mice harboring these mutations exhibit a pleiotropic syndrome characterized by yellow coat color, obesity, hyperglycemia, hyperinsulinemia, and increased susceptibility to hyperplasia and carcinogenesis in numerous tissues, including the liver. The goal of this research was to determine if ectopic expression of the agouti gene in the liver alone is sufficient to recapitulate any aspect of this syndrome. For this purpose, we generated lines of transgenic mice expressing high levels of agouti in the liver under the regulatory control of the albumin promoter. Expression levels of the agouti transgene in the liver were quantified by Northern blot analysis. Functional agouti protein in the liver of transgenic mice was assayed by its ability to inhibit binding of the alpha-melanocyte stimulating hormone (alphaMSH) to the Mc1r. Body weight, plasma insulin and blood glucose levels were analyzed in control and transgenic mice. Control and transgenic male mice were given a single intraperitoneal injection (10 mg/kg) of the hepatocellular carcinogen, diethylnitrosamine (DEN), at 15 days of age. Mice were euthanized at 36 or 40 weeks after DEN injection and the number of tumors per liver and total liver weights were recorded. RESULTS: The albumin-agouti transgene was expressed at high levels in the livers of mice and produced a functional agouti protein. Albumin-agouti transgenic mice had normal body weights and normal levels of blood glucose and plasma insulin, but responded to chemical initiation of the liver with an increased number of liver tumors compared to non-transgenic control mice. CONCLUSIONS: The data demonstrate that liver-specific expression of the agouti gene is not sufficient to induce obesity or diabetes, but, in the absence of these factors, agouti continues to promote hepatocellular carcinogenesis.

Agouti Signaling Protein↗

PubMed2004

The knockout mouse project.

Mouse knockout technology provides a powerful means of elucidating gene function in vivo, and a publicly available genome-wide collection of mouse knockouts would be significantly enabling for biomedical discovery. To date, published knockouts exist for only about 10% of mouse genes. Furthermore, many of these are limited in utility because they have not been made or phenotyped in standardized ways, and many are not freely available to researchers. It is time to harness new technologies and efficiencies of production to mount a high-throughput international effort to produce and phenotype knockouts for all mouse genes, and place these resources into the public domain.

Alleles↗

PubMed2003

Loss of the Tg737 protein results in skeletal patterning defects.

Tg737 mutant mice exhibit pathologic conditions in numerous tissues along with skeletal patterning defects. Herein, we characterize the skeletal pathologic conditions and confirm a role for Tg737 in skeletal patterning through transgenic rescue. Analyses were conducted in both the hypomorphic Tg737(orpk) allele that results in duplication of digit one and in the null Tg737(delta2-3betaGal) allele that is an embryonic lethal mutation exhibiting eight digits per limb. In early limb buds, Tg737 expression is detected throughout the mesenchyme becoming concentrated in precartilage condensations at later stages. In situ analyses indicate that the Tg737(orpk) mutant limb defects are not associated with changes in expression of Shh, Ihh, HoxD11-13, Patched, BMPs, or Glis. Likewise, in Tg737(delta2-3betaGal) mutant embryos, there was no change in Shh expression. However, in both alleles, Fgf4 was ectopically expressed on the anterior apical ectodermal ridge. Collectively, the data argue for a dosage effect of Tg737 on the limb phenotypes and that the polydactyly is independent of Shh misexpression.

Animals↗

PubMed2002

Molecular and phenotypic analysis of 25 recessive, homozygous-viable alleles at the mouse agouti locus.

Agouti is a paracrine-acting, transient antagonist of melanocortin 1 receptors that specifies the subapical band of yellow on otherwise black hairs of the wild-type coat. To better understand both agouti structure/function and the germline damage caused by chemicals and radiation, an allelic series of 25 recessive, homozygous-viable agouti mutations generated in specific-locus tests were characterized. Visual inspection of fur, augmented by quantifiable chemical analysis of hair melanins, suggested four phenotypic categories (mild, moderate, umbrous-like, severe) for the 18 hypomorphs and a single category for the 7 amorphs (null). Molecular analysis indicated protein-coding alterations in 8 hypomorphs and 6 amorphs, with mild-moderate phenotypes correlating with signal peptide or basic domain mutations, and more devastating phenotypes resulting from C-terminal lesions. Ten hypomorphs and one null demonstrated wild-type coding potential, suggesting that they contain mutations elsewhere in the > or = 125-kb agouti locus that either reduce the level or alter the temporal/spatial distribution of agouti transcripts. Beyond the notable contributions to the field of mouse germ cell mutagenesis, analysis of this allelic series illustrates that complete abrogation of agouti function in vivo occurs most often through protein-coding lesions, whereas partial loss of function occurs slightly more frequently at the level of gene expression control.

Agouti Signaling Protein↗