Rat Breeding Parameters According to Floor Space Available in Cage.

The cage floor space recommended for a female rat with a litter is greater in the 8th edition of the Guide for the Care and Use of Laboratory Animals than in previous editions. As a result, research institutions using commonly available cages to house rats may not offer the recommended amount of space for a breeding pair and litter housed in the same cage. We evaluated breeding parameters in rats housed in cages with 143 in(2) (922.6 cm(2)) compared with 210 in(2) (1355 cm(2)) of floor space. Given the strains of rats typically used at our institution, a monogamous breeding pair and litter requires 164 in(2) (1058.1 cm(2)) of floor space according to the Guide. Pairs of breeding animals were housed in each type of cage; and average time between litters, number of litters born, percentage of litter weaned, numbers of pups born and weaned, and average weaning weights were evaluated. None of the breeding parameters evaluated differed according to the floor space of the cage in which the rats were housed.

Genome-wide Association Studies Identify Genetic Loci Associated With Albuminuria in Diabetes.

Elevated concentrations of albumin in the urine, albuminuria, are a hallmark of diabetic kidney disease and are associated with an increased risk for end-stage renal disease and cardiovascular events. To gain insight into the pathophysiological mechanisms underlying albuminuria, we conducted meta-analyses of genome-wide association studies and independent replication in up to 5,825 individuals of European ancestry with diabetes and up to 46,061 without diabetes, followed by functional studies. Known associations of variants in CUBN, encoding cubilin, with the urinary albumin-to-creatinine ratio (UACR) were confirmed in the overall sample (P = 2.4 × 10(-10)). Gene-by-diabetes interactions were detected and confirmed for variants in HS6ST1 and near RAB38/CTSC. Single nucleotide polymorphisms at these loci demonstrated a genetic effect on UACR in individuals with but not without diabetes. The change in the average UACR per minor allele was 21% for HS6ST1 (P = 6.3 × 10(-7)) and 13% for RAB38/CTSC (P = 5.8 × 10(-7)). Experiments using streptozotocin-induced diabetic Rab38 knockout and control rats showed higher urinary albumin concentrations and reduced amounts of megalin and cubilin at the proximal tubule cell surface in Rab38 knockout versus control rats. Relative expression of RAB38 was higher in tubuli of patients with diabetic kidney disease compared with control subjects. The loci identified here confirm known pathways and highlight novel pathways influencing albuminuria.

Derivation and genetic modification of embryonic stem cells from disease-model inbred rat strains.

The lack of rat embryonic stem cells (ESCs) and approaches for manipulation of their genomes have restricted the ability to create new genetic models and to explore the function of a single gene in complex diseases in the laboratory rat. The recent breakthrough in isolating germline-competent ESCs from rat and subsequent demonstration of gene knockout has propelled the field forward, but such tools do not yet exist for many disease-model rat strains. Here we derive new ESCs from several commonly used rat models including the Dahl Salt Sensitive (SS), the sequenced Brown Norway (BN), and Fischer (F344) rat and establish the first germline-competent ESCs from a hypertension disease model strain, the Fawn Hooded Hypertensive (FHH) rat. Genetic manipulations including transgenesis mediated by lentivirus, routine homologous recombination, and homologous recombination mediated by zinc-finger nucleases (ZFNs) were performed effectively in FHH rat ESCs. Our results showed these rat ESC lines, isolated from inner cell masses using mechanical splitting, had germline competency; the Pparg gene locus and homologous genomic region to the mouse Rosa26 locus can be targeted effectively in these rat ESCs. Furthermore, our results also demonstrated that ZFNs increased the efficiency of proper homologous recombination in FHH rat ESCs using targeting vectors with short homology arms. These rat ESC lines and advancements in genetic manipulation pave the way to novel genetic approaches in this valuable biomedical model species and for exploration of complex disease in these strains.

Comparison of 2 rat breeding schemes using conventional caging.

Compared with earlier editions, the eighth edition of the Guide for the Care and Use of Laboratory Animals recommends more cage floor space for female rats with litters. As such, conventional rat cages often do not supply the recommended floor space to maintain 2 adult rats and a litter in the same cage. We evaluated 2 breeding schemes using traditional cages that afford 140 in.(2) (903 cm(2)) of floor space: (1) monogamous pairs housed continuously and (2) monogamous pairs cohoused intermittently with removal of the male rat after parturition. The results did not demonstrate a significant difference between breeding schemes in generation time, number of litters per breeding pair, percentage of litters weaned, number of pups born per breeding pair, and number of pups weaned per breeding pair. However, the average weaning weight of pups was significantly higher with scheme 1 compared with scheme 2. Collectively, these results indicate continuous housing of monogamous breeding pairs may be preferable to intermittent housing when conventional cages are used.