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Gitelman's syndrome is an autosomal recessive disorder marked by salt wasting and hypokalaemia resulting from loss of-function mutations in the SLC12A3 gene that codes for the thiazide sensitive Na -Cl cotransporter. Gitelman's syndrome is usually distinguished from Bartter's syndrome by the presence of both hypomagnesaemia and hypocalciuria. The human SLC12A3 gene, which is located on chromosome 16, consists of 26 exons and encodes a protein that contains 12 putative transmembrane domains with long intracellular amino and carboxy termini. In the present study, we developed a method of genetic diagnosis for Gitelman's syndrome using DNA sequencing. A patient was found to be a compound heterozygote with a single base substitution at nucleotide 2552 (CTC-to-CAC, L849H) and a substitution at nucleotide 2561 (CGC-to-CAC, R852H) in exon 22. Familial linkage analysis confirmed that 849H was the paternal allele and 852H was the maternal allele. The method can save time and costs, and it should be useful for genetic testing in clinical laboratory of every hospital.

Genetic dissection of diseases is one of the epoch-making achievements in modern medicine. Positional cloning is a key method to isolate disease-related genes. For positional cloning, there are two conventional methods: family-based studies and case-control studies. In this review, I would like to describe several family-based studies on single gene diseases which I had conducted including those of Akita diabetic mice, systemic carnitine deficiency and Hartnup disease. The study of systemic carnitine deficiency underscored a potential power of the "Carrier state." Furthermore, cultural and public health practices in Japan such as preservation of umbilical cords and mother and child passbooks enabled us to conduct linkage analysis even 20 years after the deaths of affected patients in Hartnup disease. For multifactorial diseases, I present three family-based studies: intracranial aneurysm, moyamoya and arteriovenous malformation. Finally, I discuss on theoretical issues concerning the relationship among odds ratio, phenocopy rate and penetrance by formulating a single-locus dominant association model. Analysis of the model predicted a notion that a large odds ratio facilitates familial clustering of multifactorial diseases and vice versa is the case. Furthermore, the analysis predicted that genetic markers for screening should have odds ratio >/= eight to maintain similar qualities commonly required for clinical tests. Collectively, the analysis predicted a two-stage study design composed of linkage analysis based on a family study and subsequent replication by a case-control association study is more rational than the currently used two-independent case-control design. This newly proposed method is expected to provide polymorphisms, which have large odds ratios, requiring only minimum research budgets.

The disease-specific chromosomal abnormalities can be observed in various hematological malignancies, detected by chromosome analysis and/or genetic testing. Genetic testing enables the accurate diagnosis of the type of leukemia resulting from chromosome translocation and hence is useful for the choice of adequate treatment. Furthermore, genetic testing allows the detection of minimal residual disease (MRD) due to its high sensitivity. In recent years, a lot of information has been gained on the evaluation of MRD, e.g., the amount of MRD corresponding to morphological recurrence or requiring the treatment. Thus, the usefulness of MRD quantification at genetic level by real-time PCR has been established. At present, however, there is no standard laboratory procedure for leukemia genetic testing. Here, the problems related to external precision management of this new test are also discussed.

Haplotype map is the basis of SNP association studies in two aspects. One is to understand how SNPs are organized on chromosomes, thereby helping researchers to select tag SNPs to be examined. The other is to explore the presence of "hidden SNP" by haplotype analyses that is really associated with the disease. Although it is very difficult to forecast the future of SNP studies, the final and ideal methodology should be high--throughput whole genome sequencing with low price. At such stage, data mining technique will be very important since huge amount of genotype data should be handled and analyzed.

Subarachnoid hemorrhage (SAH) due to rupture of an intracranial aneurysm (IA) is a devastating condition with high mortality and morbidity. Genetic as well as environment factors play important roles in the pathogenesis of SAH and IAs. We review the present knowledge on the genetic factors responsible for SAH or IAs. Linkage analysis and association study are used for genetic dissection. Genome-wide linkage analyses have specified several genetic loci for IAs and 6 loci (1p34-36, 7q11, 11q24-25, 14q22-31, 19q13, and Xp22) have been replicated in different populations. Numerous functional and/or positional candidate genes for IAs have been investigated by case-control association studies. The results of genetic association studies are modest because of small sample sizes. To date, no specific genes have been identified as responsible for IA development or rupture. Recent, large-scale genome-wide association (GWA) studies have revealed consistent and replicable genetic markers of several complex diseases such as coronary artery disease and type 2 diabetes. Although, thus far, no GWA studies have been performed for IAs, such a study may accomplish the breakthrough of genetic dissection of IAs. The identification of susceptible genes might lead to the understanding of the mechanism of IA formation or rupture and to novel therapeutic strategies.

Cerebral cavernous malformations (CCMs) are vascular lesions of the central nervous system that consisit of enlarged vascular channels without intervening normal parenchyma. The CCMs can occur as sporadic or autosomal-dominant inherited condition. Linkage analysis of the familial CCMs has identified three different loci at 7q21.2 (CCM1), 7q13 (CCM2), and 3q25.2-q27 (CCM3). The genes at these loci have been identified as Krev1 Interaction Trapped 1; KRIT1 (CCM1), MGC4607; malcavernin (CCM2), and PDCD10 (CCM3), respectively. Recent investigations on these genes suggest that there are interactions between each gene, although the exact pathway of the formation of CCMs is still undetermined. In this review, the authors summarize the currently avaliable knowledge on the molecular events associated with CCMs.

Moyamoya disease (MMD) is characterized by progressive stenosis and occlusion of the terminal portion of the bilateral carotid arteries as well as arterial collateral vessels. The etiology of MMD, however, remains unknown. Several pieces of evidence suggest the involvement of genetic factors in MMD: over 10% of MMD patients have affected blood relatives; concordance in the affection status has been proven in 80% of identical twins; and there is an ethnic predisposition to MMD, the incidence of the disease being the highest in the Asian population. With regard to genetic factor (s), transmission of MMD does not follow the classic Mendelian law, i.e., skipping of a generation and discordance in identical twins, thereby indicating that genetic influence is likely to determine the susceptibility to MMD. This study aimed to overview the recent findings related to the genetic determinants in MMD and to provide research perspectives for the next decade. Pathophysiological investigations at molecular levels have uncovered the upregulation of various growth and stress response factors that are associated with angiogenesis in occlusive cerebral arteries.

Identification of the genetic polymorphisms that contribute to susceptibility for schizophrenia have focused on the technique of genetic linkage, but now whole-genome association studies are becoming more feasible. Linkage analyses in families collected from different populations have provided relatively well-defined genomic loci. These have been typically followed by fine mapping studies using single nucleotide polymorphisms (SNPs). In this article, we review the current genetic evidence that implicates schizophrenia-susceptibility genes. Recently, it has been reported that more than 70% of genome regions are transcribed. From this point of view, the genetic study for identification of susceptive genes proceeds to another aspect of genome research.

There are several different types of repeated sequences in the genome of Candida albicans, including the MRS (Major repeated sequence). In 2004, the whole genome sequence of C. albicans was published. Assembly of the sequences to chromosomal length contigs was not achieved, mainly due to interruption of the sequences by MRS. However, MRS including Ca3, 27A and RPS have been playing important roles in a number of epidemiological studies and basic biological investigations into C. albicans chromosome loss events and associated phenotypic changes. Here we summarize structural analyses from subrepeat sequences to the chromosome level, and functional analyses of MRS.

With the recent advances in DNA sequencing technology, a succession of entire genome sequences have been published. A number of genome projects are underway in pathogenic fungi. From these, we present the history and current status of the genomic analysis of Candida albicans. The sequencing project for this organism has been undertaken at Stanford University, and is now nearing the end.