Abstract
Self-renewing spermatogonial stem cells are present in the testis throughout the life of male mammals. Recent studies at the University of Pennsylvania showed that murine spermatogonial stem cells could be isolated from neonatal or adult testes, transduced in vitro by retroviral vectors carrying exogenous genes, and transplanted into the testes of infertile recipient mice, thus rendering the recipient mice fertile. Transgenes introduced into spermatogonial stem cells were expressed in recipient testes and in offspring of recipient mice. Compared to genetic engineering strategies based on female germ cells, this technique did not markedly improve the efficiency of generating transgenic mice or shorten the time required to produce the mice; however, spermatogonial stem cells are readily available from a variety of species and can be cryopreserved, making them potentially valuable for genetic manipulation.
Nagano M, Brinster CJ, Orwig KE, Ryu BY, Avarbock MR, Brinster RL: Transgenic mice produced by retroviral transduction of male germ-line stem cells. Proc Natl Acad Sci USA 98: 13090–13095, 2001
Dr. Bert Vogelstein and his associates have identified a tyrosine phosphatase, PRL-3, that is expressed at higher levels in metastatic colon cancer cells than in nonmetastatic tumor cells or normal colon epithelium. The PRL-3 gene was isolated using immunoaffinity techniques to purify metastatic tumor cells and serial analysis of gene expression (SAGE). A total of 144 transcripts were specifically elevated in metastatic cells. Thirty-eight of these transcripts were studied in detail; only PRL-3 was elevated in all metastatic tumors studied. Furthermore, the PRL-3 gene was amplified 20 to 40-fold in several metastatic tumors. PRL-3 may play an important role in colorectal metastasis, and it may constitute a potential therapeutic target.
Saha S, Bardelli A, Buckhaults P, Volculescu VE, Rago C, St. Croix B, Romans KE, Choti MA, Lengauer C, Kinzler KW, Vogelstein B: A phosphatase associated with metastasis of colorectal cancer. Science 294: 1343–1346, 2001
Ivermectin is used extensively in veterinary medicine to treat nematode and arthropod parasitism. In most mammals, the blood-brain barrier prevents access of ivermectin to the central nervous system. One of the proteins responsible for maintaining an effective blood-brain barrier is P-glycoprotein, which is encoded by the multi-drug-resistance gene, mdr1. Up to 50% of Collie Dogs are highly sensitive to the neurotoxic effects of ivermectin. Investigators at Washington State University showed that one population of ivermectin-sensitive Collies was homozygous for a four-nucleotide deletion in the mdr1 gene; this deletion generated a stop codon leading to truncation of the protein. Collies in the same kennel that were homozygous for the wild-type allele of mdr1 or were heterozygous for the mutation were ivermectin-resistant.
Mealey KL, Bentjen SA, Gay JM, Cantor GH: Ivermectin sensitivity in collies is associated with a deletion mutation of the mdr1 gene. Pharmacogenetics 11: 727–733, 2001
Tissue microarrays have several features that make them valuable for detecting associations between molecular markers and prognosis: they facilitate speedy analysis of very large numbers of samples, they permit rigorous standardization of analysis techniques, and they maximize the number of analyses that can be performed on a given set of samples. To establish the reliability of tissue microarrays for screening potential molecular markers of tumor prognosis, an international group of scientists examined the expression of three prognostic markers (estrogen receptor, progesterone receptor, and p53) by immunohistochemistry in a group of 553 human breast cancers. They determined that results obtained by examining the small tumor samples included on tissue microarrays were comparable to those obtained using larger tumor samples. Thus, tumor heterogeneity, at least for the markers examined, did not limit the usefulness of tissue microarrays. Nonetheless, including multiple punches from each tumor on a microarray increases the number of interpretable tumors.
Torhorst J, Bucher C, Kononen J, Haas P, Zuber M, Kochi OR, Mross F, Dieterich H, Moch H, Mihatsch M, Kallioniemi OP, Sauter G: Tissue microarrays for rapid linking of molecular changes to clinical endpoints. Am J Pathol 159: 2249–2256, 2001
In humans, disproportionate accumulation of visceral fat is associated with insulin resistance, glucose intolerance, and dyslipidemia (the metabolic syndrome). Adipocytes from obese humans have increased 11β hydroxysteroid dehydrogenase type 1 activity, that is believed to cause tissue-specific amplification of glucocorticoid activity. Transgenic mice that overexpressed 11β hydroxysteroid dehydrogenase type 1 in adipose tissue developed a spectrum of lesions, including visceral obesity, insulin-dependent diabetes, and hyperlipidemia, similar to that seen in humans with visceral obesity and the metabolic syndrome. Furthermore, these mice were hyperphagic. Based on these findings, it was suggested that 11β hydroxysteroid dehydrogenase type 1 may be a potential molecular target for obesity treatment.
Masuzaki H, Paterson J, Shinyama H, Morton NM, Mullins JJ, Seckl JR, Flier JS: A transgenic model of visceral obesity and the metabolic syndrome. Science 294: 2166–2170, 2001