Descriptions and Methods of Study in Selected Genetic Isolates of Dagestan

Dagestan has unique ethnic diversity—it contains 26 indigenous ethnic groups living in the same highland regions more than 10 K years, according to archeological data. Dagestan occupies 50,300 km2 and stretches diagonally along the Great Caucasus Mountain Range. The republic is divided into three significant geographic zones: mountainous, sub-mountainous, and plains. Dagestan has been invaded often due to its strategic location. However, such invasions could not assert their authority in the Dagestan ethnic mountaineers. Unable to establish viable agriculture, these mountain villages developed artisan trades; men would furthermore leave their villages seasonally to search for work in cities and remote areas. The mountainous areas of Dagestan produced their most famous unique crafts: weapons, silversmith and goldsmith jewelry, leather, ceramic arts, carpets, and clothes. In this book, we describe our study of genetics of schizophrenia in four genetic isolates with three ethnic backgrounds, where we ascertained extended pedigrees with aggregation of the diseases. All affected cases were diagnosed previously during hospitalizations in Republican psychiatric hospitals where ICD-10 criteria were used, and in our expeditions where clinical diagnoses were refined using the DIGS, which is translated into Russian and based on DSM-IV criteria. Results showed that the epidemiological Lifetime Morbid Risk (LMR) index of schizophrenia in Dagestani isolates varies from 2 to 5 % which exceeded the known global values of 0.8 % for 2–6 times. We developed our genealogy data collection methods that allowed collections of extended pedigrees in the isolates with 300–700 members spanning 9–14 generations. As a rule, these extensive pedigrees have 2–4 founders in the most demographically old isolates and all affected members of current generations are located in one large pedigree with common ancestors. Candidates were informed of the objectives of the study in writing, and all subjects subsequently volunteered to participate. The Dagestan IRB approved the objectives of the study and Consent and Assent forms with isolates members.