RESUMEN
A whole-genome radiation hybrid (RH) panel was used to construct a high-resolution map of the rat genome based on microsatellite and gene markers. These include 3,019 new microsatellite markers described here for the first time and 1,714 microsatellite markers with known genetic locations, allowing comparison and integration of maps from different sources. A robust RH framework map containing 1,030 positions ordered with odds of at least 1,000:1 has been defined as a tool for mapping these markers, and for future RH mapping in the rat. More than 500 genes which have been mapped in mouse and/or human were localized with respect to the rat RH framework, allowing the construction of detailed rat-mouse and rat-human comparative maps and illustrating the power of the RH approach for comparative mapping.
Asunto(s)
Marcadores Genéticos/genética , Genoma , Ratas/genética , Animales , Mapeo Cromosómico , Cromosomas/genética , Genes/genética , Humanos , Células Híbridas , Ratones , Datos de Secuencia MolecularRESUMEN
To identify genetic determinants relevant to non-insulin-dependent diabetes mellitus (NIDDM), we performed a genome-wide analysis for quantitative trait loci (QTLs) using 359 backcross progeny of the Otsuka Long-Evans Tokushima Fatty (OLETF) rat. The OLETF strain is a well-studied animal model of obese NIDDM, with features of hyperinsulinemia, hyperglycemia, insulin resistance, and abundant abdominal fat. Our extensive genomic scanning with 218 markers revealed nine significant QTLs, including a strong determinant of obesity on chromosome 1 (Dmo1: LOD = 13.99, for body weight). Two highly significant QTLs for glucose homeostasis were found, one on chromosome 1 (Dmo4 LOD = 7.16, for postprandial glucose level) and the other on chromosome X (Dmo11/Odb1: LOD = 7.81, for postprandial glucose level). These data are comparable to results of our previous studies of the OLETF rat.
Asunto(s)
Diabetes Mellitus Tipo 2/genética , Carácter Cuantitativo Heredable , Tejido Adiposo , Animales , Glucemia/metabolismo , Peso Corporal , Mapeo Cromosómico , Cruzamientos Genéticos , Modelos Animales de Enfermedad , Femenino , Ligamiento Genético , Genotipo , Escala de Lod , Masculino , Obesidad/genética , Fenotipo , Ratas , Ratas Endogámicas BN , Ratas Endogámicas OLETF , Cromosoma X/genéticaRESUMEN
An Otsuka Long-Evans Tokushima Fatty (OLETF) strain of rat spontaneously developed hyperglycemia, hyperinsulinemia, insulin resistance and mild obesity, which had been studied as animal model for type II diabetes mellitus (T2DM). Recently, we observed that this strain coincidentally developed atypical hyperplasia of the choledocho-pancreatic ductal epithelium with a complete incidence. In an effort to locate genes responsible for this hyperplasia, we prepared 288 backcross progeny from a mating between OLETF rats and BN rats (which do not develop hyperplasia), and performed a genome-wide scan using 207 polymorphic genetic markers. We observed a prominent association of hyperplasia with a region involving a marker locus D14Mit4 (P = 0.00020, Fisher's exact test) and Cckar (the cholecystokinin-A receptor gene; P = 0.00025, Fisher's exact test) which is known to be disrupted in an OLETF strain. Our findings indicated that epithelial hyperplasia of the choledocho-pancreatic duct is associated with a region on rat chromosome 14 around the Cckar gene in an additive fashion with another two susceptible loci, each on chromosome 9 and 7. This implied the possibility that Cckar deficiency could result in a predisposition towards pancreatic duct hyperplasia.
Asunto(s)
Lesiones Precancerosas/genética , Receptores de Colecistoquinina/genética , Animales , Mapeo Cromosómico , Cruzamientos Genéticos , ADN/análisis , Diabetes Mellitus Tipo 2/genética , Modelos Animales de Enfermedad , Femenino , Hiperplasia/genética , Hiperplasia/patología , Endogamia , Masculino , Conductos Pancreáticos , Reacción en Cadena de la Polimerasa , Lesiones Precancerosas/patología , Ratas , Ratas Long-EvansRESUMEN
Altered lipid metabolism is closely associated with diabetes in humans, although predisposing genetic factors that affect hyperlipidemia have not yet been clarified. Our previously established OLETF strain is an obese rat model of type II diabetes, exhibiting hypertriglycemia as well as hyperinsulinemia, hyperglycemia, insulin resistance, and abundant abdominal fat. To identify genetic factors responsible for dyslipidemic phenotypes in OLETF rats, we performed a whole-genome scan using 293 male (OLETF x BN) x OLETF backcross rats. Our analysis identified two significant quantitative trait loci (QTLs), on rat chromosomes 1 and 8, that are related to fasting triglyceride levels. The chromosome 1 QTL colocalized with Dmo1 (diabetes mellitus, OLETF type 1), a locus previously shown to associate strongly with both fat levels and body weight. The other significant QTL localizes to the chromosome 8 marker D8Mit2, in a region where several apo-lipoprotein genes are clustered.
Asunto(s)
Diabetes Mellitus Tipo 2/genética , Hipertrigliceridemia/genética , Obesidad/genética , Triglicéridos/sangre , Animales , Peso Corporal/genética , Mapeo Cromosómico , Cromosomas/genética , Cruzamientos Genéticos , Diabetes Mellitus Tipo 2/sangre , Modelos Animales de Enfermedad , Ligamiento Genético , Hipertrigliceridemia/sangre , Escala de Lod , Masculino , Obesidad/sangre , Fenotipo , Carácter Cuantitativo Heredable , Ratas , Ratas Endogámicas BN , Ratas Endogámicas OLETFRESUMEN
1. The Otsuka Long-Evans Tokushima Fatty (OLETF) rat is a model of type II diabetes with accompanying dyslipidaemia and obesity. 2. To define chromosomal intervals associated with obesity (abdominal fat weight and plasma leptin levels), dyslipidaemia (plasma triglyceride, cholesterol and free fatty acids) and hyperglycaemia (plasma glucose levels), we have performed genome-wide quantitative traits loci (QTL) analyses of 115 male OLETF x (OLETF x Fischer 344) backcross animals at 16 weeks of age. 3. The Diabetes Mellitus OLETF type I (Dmo1) locus on rat chromosome 1 showed statistically significant involvement in elevations of plasma levels of triglycerides (P = 4.87 x 10(-6) at D1Rat90) and total cholesterol (P = 1.16 x 10(-5) at D1Rat306). 4. No other loci produced significant linkage to these observed phenotypes. 5. These analyses have confirmed the importance of Dmo1 in lipid homeostasis at younger ages as well as during overt diabetes, which appears later. Thus, alterations at the Dmo1 locus are a major risk factor for pathogenesis in the strain, a finding that agrees with physiological studies that indicate a role for dyslipidaemia in the type II diabetic syndrome of OLETF rats.
Asunto(s)
Mapeo Cromosómico , Hiperlipidemias/genética , Metabolismo de los Lípidos , Obesidad/genética , Carácter Cuantitativo Heredable , Animales , Colesterol/sangre , Femenino , Marcadores Genéticos , Genotipo , Hiperlipidemias/sangre , Lípidos/sangre , Masculino , Obesidad/sangre , Fenotipo , Reacción en Cadena de la Polimerasa , Ratas , Ratas Endogámicas F344 , Ratas Long-Evans , Triglicéridos/sangreRESUMEN
1. Whole-genome scans have identified Dmo1 as a major quantitative trait locus for dyslipidaemia and obesity in the Otsuka Long Evans Tokushima Fatty (OLETF) rat. 2. We have produced congenic rats for the Dmo1 locus through successive back-cross breeding with diabetic OLETF rats. Marker-assisted speed congenic protocols were applied to efficiently transfer chromosomal segments from non-diabetic Brown Norway (BN) rats into the OLETF background. 3. In the fourth generation of congenic animals, we observed a substantial therapeutic effect of the Dmo1 locus on lipid metabolism, obesity control and plasma glucose homeostasis. 4. We have concluded that Dmo1 primarily affects lipid homeostasis, obesity control and/or glucose homeostasis at fasting and is secondarily involved in glucose homeostasis after loading. 5. The results of the present study show that single-allele correction of a genetic defect of the Dmo1 locus can generate a substantial therapeutic effect, despite the complex polygenic nature of type II diabetic syndromes.
Asunto(s)
Glucemia/genética , Peso Corporal/genética , Mapeo Cromosómico/métodos , Diabetes Mellitus Tipo 2/genética , Hiperlipidemias/genética , Obesidad/genética , Alelos , Animales , Animales Congénicos , Insulina/sangre , Masculino , Fenotipo , Ratas , Ratas Long-EvansRESUMEN
Whole-genome scans have identified Dmo1 as a major quantitative trait locus (QTL) for obesity and dyslipidaemia in the Otsuka Long Evans Tokushima Fatty (OLETF) rat. We have produced congenic rats for the Dmo1 locus, using marker-assisted speed congenic protocols, enforced by selective removal of other QTL regions (QTL-marker-assisted counterselection), to efficiently transfer chromosomal segments from non-diabetic Fischer 344 (F344) rats into the OLETF background. In the third generation of congenic animals, we observed a substantial therapeutic effect of the Dmo1 locus on lipid metabolism, obesity control and plasma glucose homeostasis. We conclude that single-allele correction of an impaired genetic pathway can generate a substantial therapeutic effect, despite the complex polygenic nature of type II diabetic syndromes.
Asunto(s)
Hiperglucemia/genética , Hiperlipidemias/genética , Obesidad/genética , Alelos , Animales , Glucemia/metabolismo , Mapeo Cromosómico , Cruzamientos Genéticos , Diabetes Mellitus Tipo 2/genética , Femenino , Marcadores Genéticos , Genotipo , Masculino , Fenotipo , Carácter Cuantitativo Heredable , Ratas , Ratas Endogámicas F344 , Ratas Long-Evans , Ratas MutantesRESUMEN
We have isolated more than 12,000 clones containing microsatellite sequences, mainly consisting of (CA)n dinucleotide repeats, using genomic DNA from the BN strain of laboratory rat. Data trimming yielded 9636 non-redundant microsatellite sequences, and we designed oligonucleotide primer pairs to amplify 8189 of these. PCR amplification of genomic DNA from five different rat strains yielded clean amplification products for 7040 of these simple-sequence-length-polymorphism (SSLP) markers; 3019 markers had been mapped previously by radiation hybrid (RH) mapping methods (Nat Genet 22, 27-36, 1998). Here we report the characterization of these newly developed microsatellite markers as well as the release of previously unpublished microsatellite marker information. In addition, we have constructed a genome-wide linkage map of 515 markers, 204 of which are derived from our new collection, by genotyping 48 F2 progeny of (OLETFxBN)F2 crosses. This map spans 1830.9 cM, with an average spacing of 3.56 cM. Together with our ongoing project of preparing a whole-genome radiation hybrid map for the rat, this dense linkage map should provide a valuable resource for genetic studies in this model species.