We investigated the migration patterns of hepatitis C virus (HCV) in China. Partial E1 and/or NS5B sequences from 411 volunteer blood donors sampled in 17 provinces and municipalities located in five large regions, the north-northeast, northwest, southwest, central south, and southeast, were characterized. The sequences were classified into eight subtypes (1a, n ‫؍‬ 3; 1b, n ‫؍‬ 183; 2a, n ‫؍‬ 83; 3a, n ‫؍‬ 30; 3b, n ‫؍‬ 44; 6a, n ‫؍‬ 55; 6n, n ‫؍‬ 10; 6v, n ‫؍‬ 1) and a new subtype candidate. Bayesian evolutionary analysis by sampling trees of the E1 sequences of the five major subtypes revealed distinct migration patterns. Subtype 1b showed four groups: one is prevalent nationwide with possible origins in the north-northeast; two are locally epidemic in the central south and northwest, respectively, and have spread sporadically to other regions; and the fourth one is likely linked to the long-distance dispersion among intravenous drug users from the northwest. Subtype 2a showed two groups: the larger one was mainly restricted to the northwest and seemed to show a trend toward migration via the Silk Road; the smaller one was geographically mixed and may represent descendants of those that spread widely during the contaminated plasma campaign in the 1990s. Subtype 3a exhibited three well-separated geographic groups that may be epidemically unrelated: one showed origins in the northwest, one showed origins in the southwest, and the other showed origins in the central south. In contrast, subtype 3b had a mixture of geographic origins, suggesting migrations from the southwest to the northwest and sporadically to other regions. Structurally resembling the tree for subtype 3a, the tree for subtype 6a showed four groups that may indicate migrations from the central south to southeast, southwest, and northwest. Strikingly, no subtype 6a strain was identified in the north-northeast. IMPORTANCEWith a population of greater than 1.3 billion and a territory of >9.6 million square kilometers, China has a total of 34 provinces and municipalities. In such a vast country, the epidemic history and migration trends of HCV are thought to be unique and complex but variable among regions and are unlikely to be represented by those observed in only one or at best a few provinces and municipalities. However, due to the difficulties in recruiting patients, all previous studies for this purpose have been based only on data from limited regions, and therefore, geographical biases were unavoidable. In this study, such biases were greatly reduced because we utilized samples collected from volunteer blood donors in 17 provinces and municipalities. To our knowledge, this is the first study in which the HCV isolates represented such a large portion of the country, and thus, the results should shed light on the current understanding of HCV molecular epidemiology.

Microsatellite DNA sequences consist of relatively short repeats of one to five base pair units; together with satellites and minisatellites they comprise a larger family known as tandemly repetitive sequences. Microsatellites are found both in prokaryotes and eukaryotes, including humans, wherein they appear scattered almost at random throughout the genome. Although in prokaryotes distinct biological functions have been demonstrated, the role of microsatellites in eukaryotes is less clear. Nevertheless, several interesting hypotheses exist suggesting that certain microsatellites may exert subtle influences on the regulation of gene expression. Although the presence of these subtle mechanisms may be beneficial to a whole population, when they go wrong, as is thought to happen in the case of human trinucleotide repeat associated diseases, such as Huntington's disease, the consequences for the individual can be fatal. Most human microsatellites probably have no biological use at all; however, they are extremely useful in such fields as forensic DNA profiling and genetic linkage analysis, which can be used to search for genes involved in a wide range of disorders. With a primary focus on humans, it is the aim of this review to present an up to date discussion, both of the biological aspects and scientific uses of microsatellite sequences. In the latter case, basic theoretical and technical points will be considered, and as such it may be of use both to laboratory and nonlaboratory based readers. (J Clin Pathol: Mol Pathol 2000;53:177-183) Keywords: microsatellites; genome; genetics; DNA Three billion may seem to be a very large number when used in any "normal" context. However, when used to refer to the number of repeating units of genetic information that are suYcient to encode the blueprint for something as complex as a human being, it never ceases to amaze me that this number is big enough! Consequently, it comes as even more of a surprise to find that most of these units appear to be "functionless junk"! In fact "functional DNA", consisting of transcribed genes and regions involved either in transcriptional regulation or in maintaining chromosomal structure/integrity, is thought to comprise less than a sixth of the total human genome. This observation immediately raises a considerable number of questions, namely: what is this genetic junk made up of? Is it really junk-does it truly possess no useful function either directly or indirectly? How is it acquired? What other types of organisms possess it? And can we make any use of it?Fully covering the questions raised above would provide more than ample scope for writing an entire book, and would extend well beyond the remit of this review. Nevertheless, even focusing as intended upon microsatellites and their relevance to humans, it should become clear that most of these questions remain ones that will require consideration, even if only in passing.Although only about 3% of the human genome encodes expressed protein sequences, the inclusion of non-expre...

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