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Articles by J. K Naggert
Total Records ( 2 ) for J. K Naggert
  C. E Duchesnes , J. K Naggert , M. A Tatnell , N Beckman , R. N Marnane , J. A Rodrigues , A Halim , B Pontre , A. W Stewart , G. L Wolff , R Elliott and K. G. Mountjoy

The study of spontaneous mutations in mice over the last century has been fundamental to our understanding of normal physiology and mechanisms of disease. Here we studied the phenotype and genotype of a novel mouse model we have called the New Zealand Ginger (NZG/Kgm) mouse. NZG/Kgm mice are very large, rapidly growing, ginger-colored mice with pink eyes. Breeding NZG/Kgm mice with CAST/Ei or C57BL/6J mice showed that the ginger coat colour is a recessive trait, while the excessive body weight and large body size exhibit a semidominant pattern of inheritance. Backcrossing F1 (NZG/Kgm x CAST/Ei) to NZG/Kgm mice to produce the N2 generation determined that the NZG/Kgm mouse has two recessive pigmentation variant genes (oca2p and tyrp-1b) and that the tyrp-1b gene locus associates with large body size. Three coat colors appeared in the N2 generation; ginger, brown, and dark. Strikingly, N2 male coat colour associated with body weight; the brown-colored mice weighed the most followed by ginger and then dark. The male brown coat-colored offspring reached adult body weights indistinguishable from NZG/Kgm males. The large NZG/Kgm mouse body size is a result of excessive lean body mass since these mice are not obese or diabetic. NZG/Kgm mice exhibit an unusual pattern of fat distribution; compared with other mouse strains they have disproportionately higher amounts of subcutaneous and gonadal fat. These mice are susceptible to high-fat diet-induced obesity but are resistant to high-fat diet-induced diabetes. We propose NZG/Kgm mice as a novel model to delineate gene(s) that regulate 1) growth and metabolism, 2) resistance to Type 2 diabetes, and 3) preferential fat deposition in the subcutaneous and gonadal areas.

  H Matsumura , K Kano , C. M de Evsikova , J. A Young , P. M Nishina , J. K Naggert and K. Naito

Mice homozygous for the smallie (slie) mutation lack a collagen receptor, discoidin domain receptor 2 (DDR2), and are dwarfed and infertile due to peripheral dysregulation of the endocrine system of unknown etiology. We used a systems biology approach to identify biological networks affected by Ddr2slie/slie mutation in ovaries using microarray analysis and validate findings using molecular, cellular, and functional biological assays. Transcriptome analysis indicated several altered gene categories in Ddr2slie/slie mutants, including gonadal development, ovulation, antiapoptosis, and steroid hormones. Subsequent biological experiments confirmed the transcriptome analysis predictions. For instance, a significant increase of TUNEL-positive follicles was found in Ddr2slie/slie mutants vs. wild type, which confirm the transcriptome prediction for decreased chromatin maintenance and antiapoptosis. Decreases in gene expression were confirmed by RT-PCR and/or qPCR; luteinizing hormone receptor and prostaglandin type E and F receptors in Ddr2slie/slie mutants, compared with wild type, confirm hormonal signaling pathways involved in ovulation. Furthermore, deficiencies in immunohistochemistry for DDR2 and luteinizing hormone receptor in the somatic cells, but not the oocytes, of Ddr2slie/slie mutant ovaries suggest against an intrinsic defect in germ cells. Indeed, Ddr2slie/slie mutants ovulated significantly fewer oocytes; their oocytes were competent to complete meiosis and fertilization in vitro. Taken together, our convergent data signify DDR2 as a novel critical player in ovarian function, which acts upon classical endocrine pathways in somatic, rather than germline, cells.

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