M. den Bieman

Biochemical polymorphism in the rat: Genetics of three electrophoretic variants and characterization of inbred strains

Nine inbred strains of the rat (Rattus norvegicus) were screened for differences in electrophoretically detectable proteins. Interstrain variation was observed for 7 of 26 proteins. Three of these variants have not been described previously: leucine aminopeptidase (Lap-1), major urinary protein (Mup-1), and seminal vesicle protein (Svp-2). Genetic analysis revealed two autosomal alleles for each of these polymorphisms. The loci Lap-1, Mup-1, and Svp-2 are linked neither to one another nor to the previously described Svp-1 and Es-4 loci. Each of the nine strains can be identified now by a specific set of monogenic markers.

Serum esterase genetics in rabbits. IV. The prealbumin and β-globulin systems

Discontinuous starch gel electrophoresis revealed a fourth allele of rabbit prealbumin serum esterase at locus Est-2. This allele is designated Est-2f and appears to be silent. In addition to the prealbumin serum esterases, another serum esterase system was studied in rabbits. This system is localized in the β-globulin region. Genetic analysis indicated that one locus with two codominant alleles controls the variation in this region. Linkage of this system with Est-1 and Est-2 of the prealbumin serum esterases was demonstrated. Comparison of the arrangement of these esterase loci on linkage group VI with the esterase loci on chromosome 8 of the mouse gives additional support for the theory of evolutionary conservation of chromosomal segments coding for mammalian esterases.

Genetic and physiological aspects of cholesterol accumulation in hyperresponding and hyporesponding rabbits.

After a 5 week period of feeding a cholesterol-rich diet to rabbits, hyperresponders with high plasma cholesterol levels and hyporesponders with low plasma cholesterol levels could be distinguished from normal responders. The response was found to be correlated with the esterase genotype at the Est-2 locus. The increase in total body cholesterol was higher in hyper- than in hyporesponders. In both groups most of the accumulated dietary cholesterol was found in plasma and liver. Adrenal weight and plasma corticosterone levels were more increased in hyper- than in hyporesponders. The cholesterol-rich diet resulted in an augmentation of liver lipase and lipoprotein lipase activities. These lipolytic activities were more increased in hyper- than in the hyporesponders.

Use of simple sequence length polymorphisms for genetic characterization of rat inbred strains

Genetic monitoring is an essential component of colony management and for the rat has been accomplished primarily by using immunological and biochemical markers. Here, we report that simple sequence length polymorphisms (SSLPs) are a faster and more economical way of monitoring inbred strains of rats. We characterized 61 inbred strains of rats, using primer pairs for 37 SSLPs. Each of these loci appeared to be highly polymorphic, with the number of alleles per locus ranging between 3 and 14 and, as a result, all the 61 inbred strains tested in this study could be provided with a unique strain profile. These strain profiles are also used for estimating the degree of similarity between strains. This information may provide the rationale in selecting strains for genetic crosses or for other specific purposes.

Gene mapping in the river buffalo (Bubalus bubalis L)

Somatic cell hybridization was used as a tool to examine synteny of genes in the buffalo. Parental cells were blood lymphocytes from two Egyptian river buffaloes, and cells of the HPRT(hypoxanthine phosphoribosyltransferase-negative) Chinese hamster cell line wg3h C12 (Echard et al, 1984). Hybrid cells were produced by polyethylene glycol (PEG)-mediated fusion, followed by hypoxanthine-aminopterinethymidine (HAT) selection. Twenty-one independent hybrid cell lines were established. For enzyme analysis, hybrid cells and hamster cells were lysed in lysis buffer (Meera Khan, 1971). Buffalo cardiac muscle, skeletal muscle and erythrocytes were homogenized in the same buffer, and were used as samples of reference for buffalo enzyme activity. Starch gel electrophoresis (Harris and Hopkinson, 1978) was carried out to analyze the following enzymes: glyceraldehyde-3-phosphate dehydrogenase (GAPD; EC 1.2.1.12); lactate dehydrogenase (LDH; EC 1.1.1.27); malic

Genetics of two tissue esterase polymorphisms (Est-4 and Est-5) in the rabbit

Two polymorphic esterase systems were found after electrophoresis of rabbit tissue homogenates. Each of these systems is controlled by an autosomal locus with two alleles. Est-4 determines the absence (Est-4a) or presence (Est-4b) of two bands of esterase activity with intermediate anodal mobility and broad substrate specificity. This polymorphism was found to be present in liver, small intestine, and spleen but not in kidney, heart, and testis. Est-5 is coding for cathodally migrating esterases which differ in mobility (Est-5a and Est-5b). This polymorphism was found only in kidney and testis homogenates. Est-5 esterases are more active against α-naphthyl acetate than against β-naphthyl acetate and have no activity against α-naphthyl butyrate. Linkage analysis indicated that Est-4 is localized on rabbit LG VI as part of a cluster of esterase loci, whereas Est-5 segregates independently. Rabbits from two inbred and nine partly inbred strains were tested for these polymorphisms.

Genetic analysis and mapping of biochemical markers in an F2 intercross of two inbred strains of the rabbit (Oryctolagus cuniculus).

A total of 40 biochemical and four immunological markers found to be polymorphic in the rabbit in previous studies were screened in the AX/JU and IIIVO/JU inbred strains. Although the strains are considered unrelated, only eight (biochemical) markers were found to be polymorphic between the two strains. These eight markers were analyzed in an F2 intercross population. Linkage was found for Est-5 and C on chromosome 1 and for Es-1, Est-2, Est-4, Est-6 and HP on linkage group VI. Two polymorphic markers, Es-3 and Mhr-1 could not be linked to any of the other markers.

Strain-specific response to hypercholesterolaemic diets in the rat

The cholesterolaemic effect of 2 hypercholesterolaemic diets was tested in 12 rat inbred strains. Diet I is a commercial diet supplemented with 2.0% (w/w) cholesterol and 5.0% (w/w) olive oil, diet II is identical to diet I with addition of 0.5% (w/w) sodium cholate. Strains with the highest plasma cholesterol response after diet I (BN and LEW) also had the highest cholesterol response after diet II (hyperresponders, mean response>3.5 mmol/l). In the strains DA, SHR, BC, WAC, LOU, PVG and BUF the strain mean cholesterol response remained below 1.3mmol/l after both diets (hyporesponders). Strains F344 and OM had an intermediate cholesterol response after both diets (normoresponders, mean response between 1.3 and 3.5 mmol/l). Only in the strains LOU, PVG and SHR there appeared to be a significant higher cholesterol response after diet II when compared with the cholesterol response after diet I. In the strain WKY this difference was of a borderline significance (P=0.052) and this strain turned from a normoresponder after diet I into a hyperresponder after diet II. Liver cholesterol levels as measured after feeding diet II for two weeks also appeared to be strain-specific. No correlation was found between the plasma cholesterol response after diet II and the liver cholesterol levels. Changes in plasma phospholipid and triglyceride levels have been measured for both diet I and diet II. For group means a correlation between the cholesterol response and the change in phospholipid levels was found (r=0.86 for diet I, P<0.001 and r=0.76 for diet II, P<0.01). No such correlation was found for triglyceride levels.

Segregation of genes from donor strain during the production of recombinant congenic strains

Recombinant congenic strains (RCS) constitute a set of inbred strains which are designed to dissect the genetic control of multigenic traits, such as tumour susceptibility or disease resistance. Each RCS contains a small fraction of the genome of a common donor strain, while the majority of genes stem from a common background strain. We tested at two stages of the inbreeding process in 20 RCS, derived from BALB/cHeA and STS/A, to see whether alleles from the STS/A donor strain are distributed over the RCS in a ratio as would theoretically be expected. Four marker genes (Pep-3; Pgm-1; Gpi-1 and Es-3) located at 4 different chromosomes were selected and the allelic distribution was tested after 3-4 and after 12 generations of inbreeding. The data obtained do not significantly deviate from the expected pattern, thus supporting the validity of the concept of RCS.

Chromosomal localization of genes involved in biosynthesis, metabolism or transport of cholesterol in the rat

Several genes involved in biosynthesis, transport or metabolism of cholesterol have been localized on rat chromosomes by using a radiation hybrid (RH) panel. The genes, coding for squalene epoxidase (Sqle), mevalonate kinase (Mvk), and farnesyl diphosphate farnesyl transferase 1 (Fdft1) which are involved in cholesterol biosynthesis, have been mapped on chromosome 7, 12, and 15, respectively. The genes coding for phospholipid transfer protein (Pltp), sterol carrier protein-2 (Scp2), ATP binding cassette reporter A7 (Abca7), scav- enger receptor class B, type 1 (Cd36l1), steroidogenic acute regulatory protein (Star), and lecithin:cholesterol acyl transferase (Lcat), which are involved in the transfer and/or metabolism of cholesterol, have been mapped on chromosome 3, 5, 7, 12, 16, and 19, respectively. Each of the genes Scp2, Sqle and Fdft1 maps close to a QTL for serum total cholesterol in rat, suggesting that these three genes might represent candidate genes for the previously mapped QTLs.