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Cerebral small vessel disease (CSVD) is frequently observed among the elderly and is known to cause dementia and gait disturbance associated with white matter lesions, lacunar infarcts, and cerebral hemorrhage. Molecular mechanistic studies promise to provide new insights into the pathogenesis of hereditary CSVD. Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL) is one of the hereditary CSVDs caused by a mutation in the high-temperature requirement serine peptidase A1 (HTRA1) gene. The loss of HTRA1 protease activity increases signaling via transforming growth factor (TGF)β, thereby resulting in CARASIL. Although the CARASIL has been characterized by juvenile onset alopecia and spondylosis deformans, these features are not always observed in individuals with an HTRA1 mutation. Moreover, some HTRA1 mutations cause CSVD in heterozygous states. Therefore, the clinical features of CSVD resulting from an HTRA1 mutation extend to patients with CSVD alone or to those with dominantly inherited CSVD.

Lipid metabolism is regulated by several factors, such as apolipoproteins, lipoprotein receptors, enzymes, and transfer proteins. From the early 1980s until now, molecular biology has been developing rapidly. Hence, genetic analyses have accelerated all over the world. Using these techniques, many genetic investigations have been performed in large-scale studies, which revealed the close associations between genetic abnormalities of the above-mentioned factors and a variety of dyslipidemic disorders. In recent years, novel genes which regulate cholesterol metabolism were reported. For instance, proprotein convertase subtilisin kexin type 9 (PCSK9) and autosomal recessive hypercholesterolemia (ARH) were found as causal genes in patients whose phenotypes are similar to familial hypercholesterolemia. Niemann-Pick C1-Like 1 (NPC1L1), ATP-binding cassette (ABC) A1 (ABCA1), and G5/G8 (ABCG5/G8) were also identified as cholesterol transporters in intestinal epithelial cells and hepatocytes. NPC1L1 is recognized as a target of ezetimibe, a cholesterol absorption inhibitor classified into a new class of lipid-lowering agents. However, we have not been fully successful in identifying candidate genes for all dyslipidemias. In this review, we summarize major dyslipidemic disorders and their causal genes, pathosis, clinical features, diagnosis, and therapeutic approaches. Because it is difficult to analyze genetic abnormalities in clinical laboratories at present, simple and convenient procedures for genetic analyses are expected to be developed in the near future. Such techniques may reveal unknown pathologics for heritable dyslipidemias, which may lead to the search for potential drug targets.

The discovery of the causative gene for hereditary cerebral small vessel disease (CARASIL: Cerebral Autosomal Recessive Arteriopathy with Subcortical Infarcts and Leukoencephalopathy) opens a new avenue for exploring the pathogenesis of cerebral small vessel disease. The causative gene for CARASIL is HTRA1 (high-temperature requirement A1). HTRA1 is a serine protease and inhibits TGF-β signaling in their protease activity-dependent manner. The CARASIL-associated mutant HTRA1s lost their protease activity and increase the TGF-β family signaling. However the precious molecular mechanism for inhibition of TGF-β signaling by HTRA1 has not been elucidated. We have found that HTRA1 aberrantly cleaved pro-TGF-β in an endoplasmic reticulum and the cleaved products were degraded by the endoplasmic reticulum-associated degradation pathway. The result reconfirms the importance of HTRA1 for TGF-β signaling. The study for Marfan syndrome, which is caused by the increasing TGF-β signaling in aortic artery, indicates that the angiotensin I receptor antagonist, a drug already in clinical use for hypertension, inhibits TGF-β signaling and ameliorates the disease progression in model mouse as well as patients with Marfan syndrome. In human brain, angiotensin I receptor antagonist also inhibits TGF-β signaling. Therefore angiotensin I receptor antagonist warrants investigation as a therapeutic strategy for patients with CARASIL.

Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL) is a single-gene disorder directly affecting the cerebral small blood vessels, that is caused by mutations in the HTRA1 gene encoding HtrA serine peptidase/protease 1 (HTRA1). CARASIL is the second known genetic form of ischemic, nonhypertensive, cerebral small-vessel diseases with an identified gene, following CADASIL (cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy). The exact prevalence of CARASIL is currently unknown, and so far about 50 patients have been reported, most of them from Japan and two from China. Genetically no founder haplotype has been identified, and so the disease is expected to be found more widely. The main clinical manifestations are ischemic stroke or stepwise deterioration in brain functions, progressive dementia, premature baldness, and attacks of severe low back pain or spondylosis deformans/disk herniation. The most characteristic brain MRI findings are homogeneously confluent white-matter changes and multiple lacunar infarctions in the basal ganglia and thalamus. Histopathologically, CARASIL is characterized by intense arteriosclerosis, mainly in the small penetrating arteries, without granular osmiophilic materials (GOM) or amyloid deposition. CARASIL is a prototype single-gene disorder of cerebral small vessels, secondary to and distinct from CADASIL. CARASIL-associated mutant HTRA1s exhibited decreased protease activity and failed to repress transforming growth factor-β (TGF-β) family signaling, indicating that the increased TGF-β signaling causes arteriopathy in CARASIL. Therefore, HTRA1 represents another new gene to be considered in future studies of the mechanisms and therapeutic strategies of cerebral small-vessel diseases, as well as alopecia and degenerative vertebral/disk diseases.

Hypertension is a well known risk factor for cerebral small vessel disease (SVD) characterized by MRI white matter hyperintensities called "leukoaraiosis". However, the molecular basis of SVD remains to be elucidated. Both twin and family studies have shown that leukoaraiosis is the most heritable cerebrovascular phenotype with a heritability estimated to be between 55% and 71%, suggesting genetic factors for SVD. Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL) is hereditary SVD lacking hypertension. We have recently identified the causative gene, FHtrA1, for CARASIL by genome-wide linkage study and a candidate gene approach. HtrA1 is a serine protease that represses signaling by TGF-β family members. We found that mutated HtrA1 did not repress signaling by the TGF-β family members (BMP2, BMP4, and TGF-β1), resulting in vascular fibrosis with synthesis of extracellular matrix proteins. Our results indicate that disinhibition of TGF-β signaling underlies the molecular basis of CARASIL. Marfan's syndrome is an autosomal dominant connective tissue disorder caused by disinhibition of TGF-β signaling associated with FBN1 mutations. In a small cohort study, angiotensin II-receptor blockers (ARBs) therapy in patients with Marfan's syndrome significantly slowed the rate of progressive aortic-root dilatation. This study provides a potential for developing a therapy targeting TGF-β signaling for SVD.

CARASIL (Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy) is the second known single-gene disorder directly affecting cerebral small vessels. The acronym CARASIL was proposed by Bowler and Hachinski (1994), based on its recessive inheritance and resemblance to CADASIL (R instead of D). The first CARASIL patients were most probably described in preliminary reports in 1965-66, and later in Japanese and English articles in 1969-1976. In 1985, the author and colleagues reported on another family of three brothers with strikingly similar clinical features, including not only neurological symptoms but also recurrent acute lumbago and premature alopecia, and cerebral white matter disease on CT scans, proposing that these characteristics can constitute a new systemic syndrome. According to our clinical and pathological/neuroradiological criteria, similar patients have been reported, almost exclusively from Japan, with a total reaching 50 until today. In five consanguineous families including ours, Hara et al. (2009) identified homozygous mutations in the HTRA1 gene on chromosome 10q25. Since no founder haplotype has been identified, the author and allied researchers suspect that this disorder will be found more widely. This review summarizes the historical background, epidemiology, characteristic clinical findings, neuroimaging, and clinical perspectives after the gene identification of this disorder.

Ischemic cerebral small-vessel disease is a common disorder in the elderly. However, little is known about the molecular basis of ischemic cerebral small-vessel disease. We recently found that mutations in the HtrA serine peptidase 1 (HTRA1) gene cause cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL). CARASIL is characterized by nonhypertensive cerebral small-vessel arteriopathy with alopecia and spondylosis. On neuropathologic examination, arteriosclerosis associated with intimal thickening and dense collagen fibers, loss of vascular smooth muscle cells, and hyaline degeneration of the media are observed in cerebral small arteries. These pathologic findings resemble those observed in patients with nonhereditary ischemic cerebral small-vessel disease. HTRA1 belongs to the HTRA protein family, the members of which have dual activities as chaperones and serine proteases. Studies have shown that members of the HTRA family repress transforming growth factor-Beta (TGF-Beta) family signaling. We found that CARASIL-associated mutant HTRA1s exhibited decreased protease activity and failed to repress TGF-Beta family signaling. Moreover, the amount of TGF-Beta1 was increased in the cerebral small arteries of CARASIL patients. In addition, the level of expression of ED-A fibronectin and versican, which is induced by TGF-Beta signaling, were accumulated in cerebral small arterial walls of a patient with CARASIL. Thus, we have concluded that the increased TGF-Beta signaling causes arteriopathy in CARASIL.

The cerebral cortex is one of the most intricate structures in the vertebrate brain, and enormous expansion in size and complexity are conspicuous features in the mammalian cortex. Although how the cerebral cortex evolved from ancestor brains still remains elusive, recent advances of developmental neurobiology shed light on the molecular mechanisms underlying cortical development, and also provide novel insights into the origin of the mammalian cerebral cortex. Here I introduce classical concepts and modern theories on the process for making morphological and functional diversity of the cerebral cortex. In this review, we especially focus on possible mechanism that provide 1) morphological diversity of the amniotes' cortex, 2) expansion of the mammalian neocortical areas, and 3) advancement of human cognitive abilities, based on accumulating knowledge of the comparative brain anatomy, molecular neurobiology, anthropology and cognitive archaeology.

We investigated the angiogenic effect of chymase, an alternative angiotensin II-generating enzyme, on angiogenesis using hamster sponge implant model. Exogenous administration of angiotensin II (Ang II) or angiotensin I (Ang I) directly into the sponges enhanced angiogenesis, as determined from the hemoglobin contents in the sponge granuloma tissues. Chymostatin, an inhibitor of chymase, inhibited angiogenesis induced by Ang I but not by Ang II, suggesting the presence of a chymase-like Ang II-generating activity in the sponge granuloma. TCV-116 (5 mg/kg p.o.), an antagonist of Ang II type 1 receptor, and chymostatin suppressed bFGF-induced angiogenesis, suggesting the significance of the endogenous angiotensin system. Chymase activity in the sponge granuloma increased in parallel with the rise in hemoglobin contents induced by bFGF. We also examined the effects of direct administration of human pro-chymase gene or purified hamster chymase, and demonstrated that in vivo human pro-chymase gene transfection and direct injection of purified chymase enhanced angiogenesis, which was 50% inhibited by TCV-116. Sponge granulomas treated with Ang II was supressed by vascular endothelial growth factor (VEGF) antisense. Our results suggest that chymase enhanced angiogenesis partly through the local production of Ang II, followed by up-regulation of VEGF.

Prohormone Convertase 2 (PC2) is a specific endoprotease responsible for the processing of proinsulin to insulin. PC2 is expressed in pancreatic islets, pituitary and brain but is very low or absent in most other tissues, such as liver, spleen and kidney. To evaluate the regulated expression of the human PC2 gene we have analyzed its structure and characterized its promoter. The gene spans > 130 kilobase pairs and consists of 12 exons. Comparison with the structure of the gene encoding human furin, revealed a high degree of conservation of exon-intron junctions. The hPC2 gene was localized to chromosome 20, band p11.2. The promoter region of the PC2 gene is very G + C rich and contains six potential Sp1 binding sites but no TATA or CAAT box. Analysis of the level of chrolamphenicol acetyltransferase activity with several deletion mutants identified the region from -1100 to -539 from the translation start site as essential for the PC2 promoter activity.