Association of Fcgamma receptor IIb polymorphism with susceptibility to systemic lupus erythematosus in Chinese: a common susceptibility gene in the Asian populations

The association of Fcgamma receptor (FcgammaR) polymorphisms with systemic lupus erythematosus (SLE) has been demonstrated in various populations; however, the results have been inconsistent. We recently identified a single-nucleotide polymorphism encoding a non-synonymous substitution, Ile232Thr (I232T), of FCGR2B and its association with SLE in Japanese and in Thais. Multiple functional FcgammaR genes with polymorphisms (FCGR2A, FCGR2B, FCGR3A, and FCGR3B) cluster in 1q23, and some of them are in linkage disequilibrium (LD). To differentiate contributions from multiple-linked loci, comparison of different populations may provide useful information. In this study, we analyzed the above four FCGR polymorphisms of the Chinese patients and controls for the association with SLE. FCGR2A-H131R, FCGR2B-I232T, FCGR3A-F176V, and FCGR3B genotypes were determined in 167 Chinese patients with SLE and 129 healthy controls. Association was examined using case-control analysis. Allele frequencies of FCGR2B-232T and FCGR3A-176F were significantly increased in SLE [odds ratio (OR) = 1.67 and OR = 1.41, respectively]. Interestingly, while these alleles had a tendency of positive LD in the controls, FCGR2B-232T was in positive association with FCGR3A-176V in SLE, suggesting that these two alleles were associated with SLE in an independent manner. Comparison between SLE with and without nephritis indicated significant association of FCGR2B-232T with nephritis (OR = 2.65). When the present results were combined with our previous data on the Japanese and the Thais using meta-analytic methods, highly significant and independent association was observed for FCGR2B and FCGR3A genotypes. These results strongly suggested that FCGR2B is a common susceptibility factor to SLE in the Asians.

[Distribution of MICA microsatellite in 13 population groups of China]

The genetic data of MICA microsatellite were obtained by genotyping 577 samples in 13 population groups of China, which are Han-YN, Han-GD, Han-SD, Bai, Dai, Lahu, Li, Naxi, Sala, She, Tu, Wa and Zang-YN, with genescan. Five alleles have been observed in the population groups, which are A4, A5, A5.1, A6 and A9. A5 allele is the most frequent in all population groups except Lahu and Li, while the most frequent allele for Lahu and Li is A5. 1 and A4 respectively. The second most frequent allele is the A5.1 in Han-YN, Han-SD, Dai, Naxi, Sala, She, and Wa. The lest frequent allele for Han-YN, Han-GD, Lahu, Naxi, She, Wa is the A6 which is not observed in Li. A4 allele is the lest frequent in Han-SD, Bai, Dai, Sala, Tu, Zang-YN. The results show that the distribution of MICA microsatellite is different in these population groups, and the polymorphism information contents (PIC) of this microsatellite is high. It is a potential useful marker in the study of human origin and migration, personal identification, gene mapping and location, and disease diagnosis.

Mitochondrial DNA polymorphisms in Yunnan nationalities in China

Nucleotide sequences of the D-loop region of human mitochondrial DNA from four Yunnan nationalities, Dai, Wa, Lahu, and Tibetan, were analyzed. Based on a comparison of 563-bp sequences in 99 people, 66 different sequence types were observed. Of these, 64 were unique to their respective populations, whereas only 2 types were shared between the Lahu and Wa nationalities. The D-loop sequence variation and phylogenetic analysis suggested that the 99 mtDNA lineages were classified into eight clusters in the phylogenetic tree. All lineages that had a 9-bp deletion in the COII/tRNALYs intergenic region appeared in one cluster in the D-loop tree, suggesting a single event of the deletion in the Yunnan nationalities studied. Genetic distances, based on net nucleotide diversities between populations including Han Chinese and mainland Japanese, revealed that the Dai, Wa, Lahu, and Han Chinese are closely related to each other, while Tibetan and mainland Japanese formed a single cluster. The bootstrap probability of separation between the Dai-Wa-Lahu-Chinese clade and the Tibetan-Japanese clade was 99%, indicating that there are at least two different origins among minority groups in Yunnan province. Although the genetic distance between Tibetan and Japanese within the clade is rather long, the results may shed light on the origins of mainland Japanese.

[Genetic relationships among six Chinese populations revealed by analysis of 30 autosomal STRs]

30 autosomal STRs of 6 Chinese populations (Bai, Naxi, Tu, Sala, Han in Shandong, She) were amplified by multiplex PCRs using fluerescein-labelled primers. Shriver's Dsw was estimated on the basis of the results of the genescanning and genotyping after running unnatural PAGE of the PCRs' products on ABI 377 sequencer. Phylogenetic trees were constructed by using Neighbor-Joining and UPGMA method based on Dsw, and then the genetic relationships among them were analyzed referring to some relative informations. Our results indicated that the genetic distance between Sala and Tu is near, 0.033. But the distances between Sala and other four populations are far, over 0.12; Tu is close to Naxi and Shandong Han, and the distances are 0.038, 0.063 respectively; The distance between Bai and Han is the nearest, 0.007, but there is a distance, 0.075, between Bai and Naxi, and a far distance, 0.112, between Bai and Tu; The distance between Naxi and Han is 0.100 and the distances between She and other 5 populations are all over 0.12. In both of the NJ and UPGMA phylogenetic trees, Naxi, Tu and Sala is one cluster and Bai and Han is another cluster. She is a single branch. These results, basically consistent with 6 Chinese populations' geographic distribution and histories, can provide some genetic information to comprehensively study their origin, migration, formation and development with their historical records and archaeological evidence.

[Genetic relationship among four Yunnan populations revealed by sequence of mtDNA D-loop]

mtDNA D-loop noncoding region 16048-16569 and the following 1-41 (563 bp) in 99 individuals of four Yunnan ethnic minorities (Dai, Wa, Lahu and Tibetan) were sequenced and then a phylogenetic tree was reconstructed by Neighbor-Joining method. These 99 mtDNA lineages were classified into 3 genotype groups in the tree. All lineages with 9 bp deletion in the COII/tRAN(Lys) intergenic region were clustered in group I, some individuals of Dai, Lahu, Wa and only 2 Tibetan individuals clustered in group II, individuals of all four populations were included in group III. A phylogenetic tree of the four populations was constructed by NJ method on the basis of estimate of net genetic distance among them. Our results showed, the genetic distance among Dai, Wa and Lahu is very close, but far from Tibetan, their genetic distance is similar to their geographic distance. Although both as descendants of ancient Di-Qiang tribe in history and speaking similar language, Lahu and Tibetan are not closely related. This result indicates that there are different origins of these two populations.

[Preliminary analysis of factors causing mental retardation in China]

Analysis of the data collected from national sampling survey of the mental retarded in 1987 showed: (1) prevalence of mental retardation in China was 12.68/1,000, (2) its causes mainly included hereditary diseases, cerebral diseases, malnutrition, pregnant infection and birth trauma for children and senile dementia for the elderly aged 60 or over, (3) severe mental retardation was mainly caused by cerebral diseases and developmental deformity in the country, and (4) the causes for 40.1% of the mental retarded persons remained unknown. Based on the researches at home and abroad, a series of major preventive measures for mental retardation have been put forward, they included: (1) to promote better birth and better rearing, vaccination, proper nutrition for pregnant mothers and infants, and safety education as focuses in primary prevention, (2) to detect early and timely treat cerebral diseases and nutritional deficiency, to strengthen antenatal diagnosis and early screening for inborn metabolic diseases as secondary prevention, and (3) to strengthen education, behavioral training and psychological rehabilitation, and to provide community-based rehabilitation service for the mental retarded as tertiary prevention.