Histological and ultrastructural features in the early stage of Purkinje cell degeneration in the cerebellar calcification (CC) rat.

The cerebellar calcification (CC) rat is a new neurodegenerative mutant with severe Purkinje cell loss and symmetrical calcifications in the cerebellar cortex manifesting ataxia: lack of coordination in body movements. In the present study, histopathological features were examined in the Purkinje cell degeneration in postnatal homozygous suckling rats without clinical signs, which were genotyped by microsatellite markers. In addition, the calcified Purkinje cells were investigated ultrastructurally and elemental analysis was performed on the deposits. Body weight of the homozygous (cc/cc) rats was already slightly lower compared with the heterozygotes (cc/+) in the neonatal stage. The degeneration of the Purkinje cells in the cc/cc rats was recognized obviously in lobules VI, VII, VIII and IX from 14 days after birth, a few days before the appearance of the ataxic behavior. The Purkinje cells in the region along the fissure between the VIII and IX lobule areas were intensely positive for periodic acid-Schiff reaction specific to glycoconjugates, and in this region, calcium depositions were weakly positive for von Kossa's stain. Electron microscopy also revealed that the calcified Purkinje cells possessed numerous electron-dense bodies containing inclusions with cystic structures such as vesicles, mitochondria and lysosomes, and these bodies were mainly composed of calcium and phosphorous. These findings suggest abnormal storage of glycoconjugates might be a trigger of Purkinje cell degeneration and serves as a matrix for accumulation of calcium phosphate in the cerebellum of CC rats.

Rat mutations cvd and hob with cerebellar malformations map to chromosome 2.

In this paper, we executed genome mapping and comparative mapping analyses for cvd and hob, autosomal recessive mutations with cerebellar vermis defect and cerebellar dysplasia in the rat. For the linkage analysis, we produced three sets of backcross progeny, (ACI x CVD)F(1) and (F344 x CVD)F(1) females crossed to a cvd homozygous male rat, and (HOB x WKY)F(1) males crossed to hob homozygous female rats. Analysis of the segregation patterns of simple sequence length polymorphism (SSLP) markers scanning the whole rat genome allowed the mapping of these autosomal recessive mutations to rat Chromosome (Chr) 2. The most likely gene order is D2Mgh12 - D2Rat86 - D2Mit15 - D2Rat185 - cvd - D2Rat66 - D2Mgh13, and D2Mit18 - Fga -D2Mit14 - D2Rat16 - hob - D2Mgh13. Crossing test between a proven cvd heterozygous and a hob heterozygous rats demonstrated their allelism. Furthermore, comparative mapping indicated the cvd locus corresponds to mouse chromosome 3 and a strong candidate gene Unc5h3, a causative gene for the rostral cerebellar malformation mouse, was implicated.

A decreased expression of angiopoietin-like 3 is protective against atherosclerosis in apoE-deficient mice.

KK/Snk mice (previously KK/San) possessing a recessive mutation (hypl) of the angiopoietin-like 3 (Angptl3) gene homozygously exhibit a marked reduction of VLDL due to the decreased Angptl3 expression. Recently, we proposed that Angptl3 is a new class of lipid metabolism modulator regulating VLDL triglyceride (TG) levels through the inhibition of lipoprotein lipase (LPL) activity. In this study, to elucidate the role of Angptl3 in atherogenesis, we investigated the effects of hypl mutation against hyperlipidemia and atherosclerosis in apolipoprotein E knockout (apoEKO) mice. ApoEKO mice with hypl mutation (apoEKO-hypl) exhibited a significant reduction of VLDL TG, VLDL cholesterol, and plasma apoB levels compared with apoEKO mice. Hepatic VLDL TG secretion was comparable between both apoE-deficient mice. Turnover studies revealed that the clearance of both [3H]TG-labeled and 125I-labeled VLDL was significantly enhanced in apoEKO-hypl mice. Postprandial plasma TG levels also decreased in apoEKO-hypl mice. Both LPL and hepatic lipase activities in the postheparin plasma increased significantly in apoEKO-hypl mice, explaining the enhanced lipid metabolism. Furthermore, apoEKO-hypl mice developed 3-fold smaller atherogenic lesions in the aortic sinus compared with apoEKO mice. Taken together, the reduction of Angptl3 expression is protective against hyperlipidemia and atherosclerosis, even in the absence of apoE, owing to the enhanced catabolism and clearance of TG-rich lipoproteins.