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931.
Conservation of position and exclusive expression of mouse Xist from the inactive X chromosome 总被引:32,自引:0,他引:32
N Brockdorff A Ashworth G F Kay P Cooper S Smith V M McCabe D P Norris G D Penny D Patel S Rastan 《Nature》1991,351(6324):329-331
X-chromosome inactivation in mammals is a regulatory phenomenon whereby one of the two X chromosomes in female cells is genetically inactivated, resulting in dosage compensation for X-linked genes between males and females. In both man and mouse, X-chromosome inactivation is thought to proceed from a single cis-acting switch region or inactivation centre (XIC/Xic). In the human, XIC has been mapped to band Xq13 (ref. 6) and in the mouse to band XD (ref. 7), and comparative mapping has shown that the XIC regions in the two species are syntenic. The recently described human XIST gene maps to the XIC region and seems to be expressed only from the inactive X chromosome. We report here that the mouse Xist gene maps to the Xic region of the mouse X chromosome and, using an interspecific Mus spretus/Mus musculus domesticus F1 hybrid mouse carrying the T(X;16)16H translocation, show that Xist is exclusively expressed from the inactive X chromosome. Conservation between man and mouse of chromosomal position and unique expression exclusively from the inactive X chromosome lends support to the hypothesis that XIST and its mouse homologue are involved in X-chromosome inactivation. 相似文献
932.
Identification and mapping to chromosome 1 of a susceptibility locus for periinsulitis in non-obese diabetic mice 总被引:11,自引:0,他引:11
Insulin-dependent diabetes mellitus (IDDM) is a polygenic disease caused by autoimmune destruction of insulin-producing beta cells in the islets of Langerhans. Its onset is preceded by a long and variable period in which lymphoid cells infiltrate the pancreas but first remain outside the islets (peri-insulitis) before invading them (insulitis). Among susceptibility loci, only the major histocompatibility complex (MHC) has been clearly assigned. Genetic study of the nonobese diabetic (NOD) mouse model for insulin-dependent diabetes mellitus has revealed genetic linkage of insulitis and of early onset diabetes with two non-MHC loci mapping to chromosome 3 and 11 respectively. Here we report a close association of periinsulitis with a third non-MHC locus mapping to chromosome 1. Successive stages in the progression of diabetic disease thus appear to be controlled by distinct genes or sets of genes. 相似文献
933.
934.
F. R. Brush 《Cellular and molecular life sciences : CMLS》1991,47(10):1039-1050
Bidirectional genetic selection for good and poor active avoidance learning in a shuttle box has been carried out in three independent laboratories using remarkably similar discrete-trial training procedures. The resulting strains are known as the Roman High and Low Avoidance (RHA and RLA), the Syracuse High and Low Avoidance (SHA and SLA) and the Australian High and Low Avoidance (AHA and ALA) strains, respectively. An additional unidirectionally selected strain, known as the Tokai High Avoider (THA) strain was developed in Japan using a free-operant Sidman avoidance procedure in a Skinner box. This paper reviews the selection of the Syracuse strains, enumerates the various behavioral and endocrine characteristics of the strains, and compares them to the other similarly selected strains. The behavioral work suggests that genetic selection from diverse breeding stocks has resulted in common characteristics that differentiate the strains in the emotional, not learning, domain. The endocrine data, however, are somewhat at odds. The Syracuse strains differentiate one way with respect to endocrine function, and the Roman strains differentiate in the opposite way. We suggest, therefore, that the endocrine correlates are not tightly linked to the avoidance genotype. Genetic analysis of all of the selected strains for both the avoidance phenotype and the endocrine correlates will be needed to test this hypothesis.Preparation of this paper was supported by research grant MH-39230-3 from the National Institute of Mental Health. 相似文献
935.
The median procedure for n-trees as a maximum likelihood method 总被引:1,自引:1,他引:0
F. R. McMorris 《Journal of Classification》1990,7(1):77-80
A few axioms are presented which allow the median procedure for n-trees to be given a maximum likelihood interpretation.Research supported by grant number N00014-89-J-1643 from the Office of Naval Research. The author would like to thank the referees for their helpful comments. 相似文献
936.
Specific expression of a foreign beta-globin gene in erythroid cells of transgenic mice 总被引:4,自引:0,他引:4
The globin gene family represents an attractive system for the study of gene regulation during mammalian development, as its expression is subject to both tissue-specific and temporal regulation. While many aspects of globin gene structure and expression have been described extensively, relatively little is known about the cis-acting DNA sequences involved in the developmental regulation of globin gene expression. To begin to experimentally define these regulatory sequences, we have taken the approach of introducing cloned globin genes into the mouse germ line and examining their expression in the resulting transgenic animals. Here we describe a series of transgenic mice carrying a hybrid mouse/human adult beta-globin gene, several of which express the gene exclusively or predominantly in erythroid tissues. These studies demonstrate that regulatory sequences closely linked to the beta-globin gene are sufficient to specify a correct pattern of tissue-specific expression in a developing mouse, when the gene is integrated at a subset of foreign chromosomal positions. 相似文献
937.
938.
Genetic variation in the New World: Ancient teeth,bone, and tissue as sources of DNA 总被引:7,自引:0,他引:7
D. A. Merriwether F. Rothhammer R. E. Ferrell 《Cellular and molecular life sciences : CMLS》1994,50(6):592-601
Examination of ancient and contemporary Native American mtDNA variation via diagnostic restriction sites and the 9-pb Region V deletion suggests a single wave of migration into the New World. This is in contrast to data from Torroni et al.34 which suggested two waves of migration into the New World (the NaDene and Amerind). All four founding lineage types are present in populations in North, Central, and South America suggesting that all four lineages came over together and spead throughout the New World. Ancient Native American DNA shows that all four lineages were present before European contact in North America, and at least two were present in South America. The presence of all four lineages in the NaDene and the Amerinds argues against separate migrations founding these two groups, although admixture between the groups is still a viable explanation for the presence of all four types in the NaDene. 相似文献
939.
A model for interfacial activation in lipases from the structure of a fungal lipase-inhibitor complex 总被引:37,自引:0,他引:37
A M Brzozowski U Derewenda Z S Derewenda G G Dodson D M Lawson J P Turkenburg F Bjorkling B Huge-Jensen S A Patkar L Thim 《Nature》1991,351(6326):491-494
Lipases are hydrolytic enzymes which break down triacylglycerides into free fatty acids and glycerols. They have been classified as serine hydrolases owing to their inhibition by diethyl p-nitrophenyl phosphate. Lipase activity is greatly increased at the lipid-water interface, a phenomenon known as interfacial activation. X-ray analysis has revealed the atomic structures of two triacylglycerol lipases, unrelated in sequence: the human pancreatic lipase (hPL)4, and an enzyme isolated from the fungus Rhizomucor (formerly Mucor) miehei (RmL). In both enzymes the active centres contain structurally analogous Asp-His-Ser triads (characteristic of serine proteinases), which are buried completely beneath a short helical segment, or 'lid'. Here we present the crystal structure (at 3 A resolution) of a complex of R. miehei lipase with n-hexylphosphonate ethyl ester in which the enzyme's active site is exposed by the movement of the helical lid. This movement also increases the nonpolarity of the surface surrounding the catalytic site. We propose that the structure of the enzyme in this complex is equivalent to the activated state generated by the oil-water interface. 相似文献
940.