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Biomedical subjects

Jonathan B Singer

Publications and source records attributed to Jonathan B Singer.

8 recordsLinked to original sources
PubMed2006

Genetic background determines response to hemostasis and thrombosis.

BACKGROUND: Thrombosis is the fatal and disabling consequence of cardiovascular diseases, the leading cause of mortality and morbidity in Western countries. Two inbred mouse strains, C57BL/6J and A/J, have marked differences in susceptibility to obesity, atherosclerosis, and vessel remodeling. However, it is unclear how these diverse genetic backgrounds influence pathways known to regulate thrombosis and hemostasis. The objective of this study was to evaluate thrombosis and hemostasis in these two inbred strains and determine the phenotypic response of A/J chromosomes in the C57BL/6J background. METHODS: A/J and C57Bl/6J mice were evaluated for differences in thrombosis and hemostasis. A thrombus was induced in the carotid artery by application of the exposed carotid to ferric chloride and blood flow measured until the vessel occluded. Bleeding and rebleeding times, as surrogate markers for thrombosis and hemostasis, were determined after clipping the tail and placing in warm saline. Twenty-one chromosome substitution strains, A/J chromosomes in a C57BL/6J background, were screened for response to the tail bleeding assay. RESULTS: Thrombus occlusion time was markedly decreased in the A/J mice compared to C57BL/6J mice. Tail bleeding time was similar in the two strains, but rebleeding time was markedly increased in the A/J mice compared to C57BL/6J mice. Coagulation times and tail morphology were similar, but tail collagen content was higher in A/J than C57BL/6J mice. Three chromosome substitution strains, B6-Chr5A/J, B6-Chr11A/J, and B6-Chr17A/J, were identified with increased rebleeding time, a phenotype similar to A/J mice. Mice heterosomic for chromosomes 5 or 17 had rebleeding times similar to C57BL/6J mice, but when these two chromosome substitution strains, B6-Chr5A/J and B6-Chr17A/J, were crossed, the A/J phenotype was restored in these doubly heterosomic progeny. CONCLUSION: These results indicate that susceptibility to arterial thrombosis and haemostasis is remarkably different in C57BL/and A/J mice. Three A/J chromosome substitution strains were identified that expressed a phenotype similar to A/J for rebleeding, the C57Bl/6J background could modify the A/J phenotype, and the combination of two A/J QTL could restore the phenotype. The diverse genetic backgrounds and differences in response to vascular injury induced thrombosis and the tail bleeding assay, suggest the potential for identifying novel genetic determinants of thrombotic risk.

Journal Article↗
PubMed2005

Two quantitative trait loci for prepulse inhibition of startle identified on mouse chromosome 16 using chromosome substitution strains.

Prepulse inhibition (PPI) of acoustic startle is a genetically complex quantitative phenotype of considerable medical interest due to its impairment in psychiatric disorders such as schizophrenia. To identify quantitative trait loci (QTL) involved in mouse PPI, we studied mouse chromosome substitution strains (CSS) that each carry a homologous chromosome pair from the A/J inbred strain on a host C57BL/6J inbred strain background. We determined that the chromosome 16 substitution strain has elevated PPI compared to C57BL/6J (P = 1.6 x 10(-11)), indicating that chromosome 16 carries one or more PPI genes. QTL mapping using 87 F(2) intercross progeny identified two significant chromosome 16 loci with LODs of 3.9 and 4.7 (significance threshold LOD is 2.3). The QTL were each highly significant independently and do not appear to interact. Sequence variation between B6 and A/J was used to identify strong candidate genes in the QTL regions, some of which have known neuronal functions. In conclusion, we used mouse CSS to rapidly and efficiently identify two significant QTL for PPI on mouse chromosome 16. The regions contain a limited number of strong biological candidate genes that are potential risk genes for psychiatric disorders in which patients have PPI impairments.

Animals↗
PubMed2005

Interacting genetic loci cause airway hyperresponsiveness.

Airway hyperresponsiveness (AHR) is a key physiological component of asthma, and the genetic basis of this complex trait has remained elusive. We created recombinant congenic mice with increased naive AHR by serially backcrossing A/J mice (which have elevated naive AHR) with C57BL/6J mice and selecting for mice with an elevated naive AHR phenotype. The seventh backcross-generation hyperresponsive mice retained A/J loci in three regions. Quantitative trait linkage (QTL) analysis of 123 unselected N8 progeny demonstrated that the AHR phenotype was not associated with any single locus but was significantly associated with an interaction of loci on chromosomes 2 and 6. These findings were confirmed in an independent analysis of chromosome substitution strain mice. The identification of genomic regions containing loci causally associated with AHR and the demonstration that this trait requires their interaction have important implications for the dissection of the genetic etiology of asthma in humans.

Animals↗
PubMed2004

Mapping quantitative trait loci for anxiety in chromosome substitution strains of mice.

Anxious behavior in the mouse is a complex quantitative phenotype that varies widely among inbred mouse strains. We examined a panel of chromosome substitution strains bearing individual A/J chromosomes in an otherwise C57BL/6J background in open-field and light-dark transition tests. Our results confirmed previous reports of quantitative trait loci (QTL) on chromosomes 1, 4, and 15 and identified novel loci on chromosomes 6 and 17. The studies were replicated in two separate laboratories. Systematic differences in the overall activity level were found between the two facilities, but the presence of the QTL was confirmed in both laboratories. We also identified specific effects on open-field defecation and center avoidance and distinguished them from overall open-field activity.

Animals↗
PubMed2004

Chromosomes 6 and 13 harbor genes that regulate pubertal timing in mouse chromosome substitution strains.

Variation in the onset of puberty among inbred strains of mice suggests that quantitative trait loci (QTLs) affect neurological and hormonal aspects of sexual maturation. Taking a novel approach toward identifying factors that regulate the hypothalamic-pituitary-gonadal (HPG) axis, we evaluated pubertal timing [as assessed by vaginal opening (VO)] in two inbred strains of mice, A/J and C57BL/6J (B6), and in a panel of chromosome substitution strains (CSSs) generated from A/J and B6 mice. In each CSS, a single chromosome from A/J has been substituted in a homozygous fashion for the corresponding chromosome in B6, partitioning the A/J genome into 22 strains with a common host (B6) background. VO occurred significantly earlier in A/J compared with B6 mice. Although the majority of the CSSs assessed had a timing of VO that was similar to the progenitor B6 strain, CSSs for chromosomes 6 and 13 each displayed significantly earlier time of VO than B6 mice. F1 (B6 x CSS) mice for chromosomes 6 and 13 displayed phenotypes that were intermediate between the CSS and B6 strains, suggesting that the trait was inherited in a codominant manner. These findings demonstrate that chromosomes 6 and 13 harbor QTLs that control the timing of VO. Identification of the responsible genes may reveal factors that regulate the maturation of the HPG axis and determine the timing of puberty.

Animals↗
PubMed2004

Genetic dissection of complex traits with chromosome substitution strains of mice.

Chromosome substitution strains (CSSs) have been proposed as a simple and powerful way to identify quantitative trait loci (QTLs) affecting developmental, physiological, and behavioral processes. Here, we report the construction of a complete CSS panel for a vertebrate species. The CSS panel consists of 22 mouse strains, each of which carries a single chromosome substituted from a donor strain (A/J) onto a common host background (C57BL/6J). A survey of 53 traits revealed evidence for 150 QTLs affecting serum levels of sterols and amino acids, diet-induced obesity, and anxiety. These results demonstrate that CSSs greatly facilitate the detection and identification of genes that control the wide diversity of naturally occurring phenotypic variation in the A/J and C57BL/6J inbred strains.

Amino Acids↗
PubMed2004

A complex interaction of imprinted and maternal-effect genes modifies sex determination in Odd Sex (Ods) mice.

The transgenic insertional mouse mutation Odd Sex (Ods) represents a model for the long-range regulation of Sox9. The mutation causes complete female-to-male sex reversal by inducing a male-specific expression pattern of Sox9 in XX Ods/+ embryonic gonads. We previously described an A/J strain-specific suppressor of Ods termed Odsm1(A). Here we show that phenotypic sex depends on a complex interaction between the suppressor and the transgene. Suppression can be achieved only if the transgene is transmitted paternally. In addition, the suppressor itself exhibits a maternal effect, suggesting that it may act on chromatin in the early embryo.

Animals↗