Restriction fragment analysis of duplication of the fourth component of complement (C4A)

The two genes encoding the fourth component of complement (C4A and C4B) reside between HLA-B and HLA-DR on human chromosome 6. Two kilobases downstream from each C4 gene lies a 21-hydroxylase gene (CA21HA and CA21HB, respectively). Utilizing the method of Southern blotting and a 5'-end 2.4-kb BamHI/KpnI fragment of the C4 cDNA, we have analyzed TaqI-digested DNA from four pedigrees with one or more extended haplotypes containing a C4A duplication, as demonstrated by protein electrophoresis and segregation analysis. Two C4A protein duplications (C4A*2,A*3,C4B*QO and C4A*3,A*5,C4B*QO) segregated with two large TaqI DNA restriction fragments (7.0 and 6.0). In pedigree Fi, one individual homozygous for HLA-A3,B35,C4,DR1,DQ1,BFF,C2C,-C4A2,3,C4BQO had TaqI 7.0- and 6.0-kb restriction fragments with equal hybridization intensities as measured by two-dimensional densitometry (7.0/6.0 kb = 0.83, SD = 0.12, N = 7). A hybridization probe for the 21-hydroxylase gene also demonstrated equal gene dosage (CA21HA/CA21HB = 1.01). DNA from another individual (Ma I-2) with a different C4A gene duplication (C4A*3,A*5,C4B*QO) also had equal densitometry measurements (7.0/6.0 kb = 1.07). We conclude that two extended haplotypes from unrelated pedigrees have two C4 genes and both C4 genes encode separate C4A alleles. These findings are compatible with a gene conversion event of C4B to C4A.     

CYP21/C4 gene organisation in Italian 21-hydroxylase deficiency families

Summary A total of 33 Italian 21-hydroxylase (21-OH) deficiency families were investigated using a combination of short and long range restriction mapping of the CYP21/C4 gene cluster. The analyses revealed that large-scale length polymorphism in this gene cluster strictly conformed to a compound variable number of tandem repeats (VNTR) plus insertion system with between one and four CYP21 + C4 units and seven BssHII restriction fragment length polymorphisms (RFLPs) (75kb, 80kb, 105kb, 110kb, 135kb, 140kb and 180kb). A total of 9/66 disease haplotypes, but only 1/61 nondisease haplotypes, showed evidence of gene addition by exhibiting three or more CYP21 + C4 repeat units. Of these, two were identified in one 21-OH deficiency patient who has a total of eight CYP21 + C4 units, being homozygous for the HLA haplotype DR2 DQ2 B5 A28. This haplotype carries four CYP21 + C4 units, three of which contain CYP21A-like genes and one of which contains a CYP21B-like gene that presumably carries a pathological point mutation. Of the other gene addition haplotypes associated with 21-OH deficiency, four show three CYP21 + C4 units flanked by HLA-DR1 and HLA-B14 markers. Although such haplotypes have commonly been associated with non-classical 21-OH deficiency, three examples in the present study are unexpectedly found in two salt-wasting patients, who are respectively homozygous or heterozygous for this haplotype. Only 7/66 disease haplotypes showed evidence of a CYP21B gene deletion.     

Extended MHC haplotypes and CYP21/C4 gene organisation in Irish 21-hydroxylase deficiency families

Summary We have analysed fifteen classical 21-hydroxylase deficiency families from throughout Southern Ireland and report the serologically defined HLA-A, HLA-B, HLA-Cw, HLA-DR, C4A and C4B polymorphisms that characterize the inferred disease haplotypes. Additionally, we have used a combination of short and long range restriction mapping procedures in order to characterize the CYP21/C4 gene organization associated with individual serologically defined haplotypes. The results obtained indicate that disease haplotypes are characterized by a high frequency (33%) of CYP21B gene deletion and 8 out of 10 such deletion haplotypes are represented by the extended haplotype HLA-DR1, C4BQo, C4A3, HLA-B40(w60), HLA-Cw3, HLA-A3. Large scale length polymorphism in the CYP21/C4 gene cluster was found to conform strictly to a variable number of tandem repeats model with 4 alleles being detected. Disease haplotypes in which defective CYP21B gene expression is inferred to result from pathological point mutations show extensive diversity of associated HLA markers and include two examples of the extended HLA haplotype HLA-DR3, B8, Cw7, A1 haplotype, which has previously been reported to be negatively associated with 21-hydroxylase deficiency. One unusual disease haplotype has two CYP21 + C4 units, both of which appear to contain CYP21B-like genes.     

Pulsed field gel electrophoresis identifies a high degree of variability in the number of tandem 21-hydroxylase and complement C4 gene repeats in 21-hydroxylase deficiency haplotypes.

The human steroid 21-hydroxylase gene, CYP21B, and its closely homologous pseudogene, CYP21A, are each normally located centromeric to a complement C4 gene C4B and C4A respectively, in an organization suggesting tandem duplication of a CYP21 + C4 unit. Such an organization has been considered to facilitate gene deletion and addition events by unequal crossover between the tandem repeats. However, the large size (approximately 30 kb) of the individual CYP21 + C4 repeat units together with the difficulty in identifying reliable CYP21A- and CYP21B-specific markers has prevented direct monitoring of gene organization on individual haplotypes by conventional Southern analyses. In the present investigation we have sought to clarify the CYP21 and C4 gene organization in members of 32 British 21-hydroxylase deficiency families by employing additional experimental approaches, notably a long-range restriction mapping approach, which permits assessment through a VNTR type of analysis, of the number of CYP21 and C4 units on individual haplotypes. Our results show that there is a very high frequency (33%) of 21-hydroxylase deficiency haplotypes where functional CYP21B gene sequence has been removed as a consequence of CYP21 + C4 gene deletion while several haplotypes show evidence of gene addition. In each case that we have investigated the gene deletion and gene addition haplotypes differ in length from conventional haplotypes by integral multiples of approximately 30 kb, which strongly supports the involvement of unequal crossover mechanisms. Additionally, the comparatively frequent occurrence of CYP21 fusion genes which contain both CYP21A- and CYP21B-associated markers is suggested by the combined data from Southern analyses, long-range restriction mapping and characterization of selected regions of CYP21 genes which have been amplified in vitro.     

Deletion of complement C4 and steroid 21-hydroxylase genes in the HLA class III region

Molecular maps have been prepared of the HLA region on human chromosome 6 that includes the complement C4 and steroid 21-hydroxylase genes (21-OH), using DNA of individuals deficient (QO) in either of the two forms C4A or C4B. In all, 18 haplotypes with C4A QO were examined by Southern analysis and two had deletions of 28-30 kb that included both the C4A and 21-OHA genes. Of six C4B QO haplotypes, one had a deletion that included both the C4B and 21-OHA genes. Thus, some of the C4 null alleles are due to deletion of the gene but the majority in this sample are not. Deletion occurred in two common haplotypes suggesting that in the population as a whole, C4A deficiency is due to deletion in about one-half the C4A QO haplotypes. As duplication of C4A or C4B genes does occur, the possibility that unequal cross-over could explain the C4 deletion was examined by preparing cosmid clones from the DNA of an individual typed C4A QO. A cloned genomic fragment containing the single C4B gene was isolated and found to be similar to the homologous region of a cosmid from a normal individual carrying a C4A gene. This suggests that if a cross-over has occurred it is in a region where the two genes are identical. The biological significance of the rather frequent occurrence in the population of haplotypes with C4A or C4B deletion together with the accompanying deletion of the 21-OHA gene is discussed.     

CYP21B gene conversion and complete CYP21A gene deletion in congenital adrenal hyperplasia

We studied a family in which one out of two children presented a non-salt wasting form of CAH. Genomic DNA of the patient, his brother, his parents and a normal control were digested by the Taq I and Bgl II restriction enzymes. The fragments were electrophoresed, transferred onto a nitrocellulose membrane and hybridized with two specific probes: pC21a for the CYP21 genes and pAT-A for the C4 genes. We performed simultaneous RFLP analyses of the CYP21 and C4 genes and determined the relative hybridization intensity of the genes using scanning densitometry of the X-ray films. The affected child had a CYP21B gene conversion in the CYP21A pseudogene on one chromosome inherited from his mother and a mutated CYP21B gene on the second chromosome inherited from his father. The second maternal chromosome, inherited by the unaffected brother, presented an unusual CYP21A gene deletion without a C4A or C4B gene deletion. Although CYP21A is a pseudogene, this type of complete CYP21A gene deletion associated with a CYP21B gene conversion has never been previously described.     

Major-histocompatibility-complex gene markers and restriction-fragment analysis of steroid 21-hydroxylase (CYP21) and complement C4 genes in classical congenital adrenal hyperplasia patients in a single population

The gene CYP21B, encoding the steroid 21-hydroxylase enzyme of adrenal steroid biosynthesis, has been mapped to the human major histocompatibility complex (MHC). Deficiency of this enzyme leads to congenital adrenal hyperplasia (CAH). We report the phenotypes of the HLA and complement C4 and Bf genes, which are closely linked to the CYP21B gene, together with a detailed analysis of the CYP21 and C4 RFLP, in 17 Finnish families with CAH. The RFLP analysis with six restriction enzymes suggested that, altogether, 35% of the affected chromosomes had a CYP21B + C4B gene deletion, 9% an obvious gene conversion of the CYP21B gene to a CYP21A-like gene, and 3% a CYP21A + C4B duplication. The remaining 53% gave the RFLP patterns also found in nonaffected chromosomes. We also found that a 14.0-kb EcoRI RFLP marker of the CYP21 genes was strongly associated with the presence of a short C4B gene, suggesting that some of the RFLP markers found with the CYP21 probe may actually derive from C4B gene polymorphism. Three particular MHC haplotypes, each with a characteristic RFLP pattern, were found in many unrelated families. These three haplotypes accounted for 59% of the affected chromosomes in our study group, the rest (41%) of the affected chromosomes being distributed among various subtypes. The results suggest that, within a single, well-defined population such as in Finland, only a few CYP21B gene defects may constitute a substantial part of the affected chromosomes. This finding will help in genetic studies of CAH in such populations.     

Defective,deleted or converted CYP21B gene and negative association with a rare restriction fragment length polymorphism allele of the factor B gene in congenital adrenal hyperplasia

Summary Defects in the enzyme, steroid 21-hydroxylase, result in congenital adrenal hyperplasia (CAH), a common autosomal recessive disorder of cortisol biosynthesis. The gene encoding this protein (CYP21B) and a closely linked pseudogene (CYP21A) have been mapped in the HLA complex on chromosome 6p, adjacent to the complement genes C4B and C4A, about 80 kb from the factor B gene. Molecular analyses of patients with CAH have shown that the cause of the defect may be either a deletion, a point mutation or a conversion of the active gene. Linkage of the disease to HLA has previously been studied by several groups. We have analyzed DNAs from patients with classical and non-classical CAH and from their family members, by probing with CYP21, C4 and BF cDNAs. In 70% of the CAH haplotypes studied, the defective CYP21B gene was indistinguishable from its structurally intact corresponding gene in Southern blot analysis, and presumably bore point mutations. In the remaining chromosomes, evidence for gene conversions, deletions and various deleterious mutations of the CYP21B gene is given. Moreover, our linkage studies show that a polymorphic TaqI cleavage site in the factor B gene, recently described by us, may be a new and useful genetic marker, because we found this TaqI restriction site only in unaffected haplotypes carrying functional CYP21B genes and, therefore, in negative association with the defective CYP21B gene.     

Two distinct areas of unequal crossingover within the steroid 21-hydroxylase genes produce absence of CYP21B

We mapped crossover sites in chimeric, recombinant CYP21 genes from six patients with salt-losing congenital adrenal hyperplasia (CAH). Nucleotide sequences unique to the CYP21A pseudogene or to the active CYP21B gene were mapped using gene-specific restriction sites and oligonucleotide hybridizations. Each chimeric CYP21 gene in the CYP21-deletion linked haplotypes contained sequences near the 5' end that were characteristic of CYP21A and only a single transition from sequences of CYP21A to those of CYP21B at the 3' end. The transitions all occurred within either of two discrete regions (+470 to +999 and +1375 to +1993). All eight chimeric CYP21 genes coupled with HLA-Bw47 in five unrelated patients had the CYP21A-CYP21B sequence transition within the same gene region (+1375 to +1993). One of the three other "CYP21B deletion" haplotypes (HLA-B7) had a sequence transition within this same region, while in the other two haplotypes (HLA-B61 and HLA-B18) the transition occurred between base pairs +470 and +999. By contrast, both CYP21 genes in a haplotype containing a gene conversion of CYP21B to CYP21A contained apparent transitions between sequences of CYP21A and CYP21B. We conclude that a single, unequal crossingover between the CYP21A and the CYP21B genes yields deletion of the active CYP21 gene and salt-losing CAH and that these crossingovers do not occur randomly within the CYP21 genes of our patients.     

Gene organization of haplotypes expressing two different C4A allotypes

Summary The gene organization of C4 haplotypes expressing two different C4A allotypes with a C4B null allele (C4A3A2-BQ0 and C4A3A6BQO) was studied using Southern blot analysis with cDNA probes and restriction enzymes which give C4A and C4B locus-specific restriction fragments. These haplotypes were shown to have both a C4A and a C4B locus present, suggesting that the C4B locus expresses a C4A protein. The finding of a 21-OH A and a 21-OH B gene on the C4A3A6BQO haplotype further suggests that this haplotype has the common gene organization C4A, 21-OH A, C4B, 21-OH B. A model explaining C4 null alleles on haplotypes found to have two C4 loci is presented.     

Direct analysis of CYP21B genes in 21-hydroxylase deficiency using polymerase chain reaction amplification

Steroid 21-hydroxylase deficiency is the leading cause of impaired cortisol synthesis in congenital adrenal hyperplasia (CAH). We have studied the structure of the CYP21B gene in 30 unrelated CAH patients using the polymerase chain reaction (PCR) to differentiate the active CYP21B gene from its highly related CYP21A pseudogene. The PCR approach obviates the need to distinguish the CYP21A and CYP21B genes by restriction endonuclease digestion and electrophoresis before analysis with labeled probes. Furthermore, direct nucleotide sequence analysis of CYP21B genes is demonstrated on the PCR-amplified DNA. Gene deletion of CYP21B, gene conversion of the entire CYP21B gene to CYP21A, frame shift mutations in exon 3, an intron 2 mutation that causes abnormal RNA splicing, and a mutation leading to a stop codon in exon 8 appear to be the major abnormalities of the CYP21B gene in our patients. These mutations appear to account for 21-hydroxylase deficiency in 22 of 26 of our salt-wasting CAH patients.     

PCR-based detection of the CYP21 deletion and TNXA/TNXB hybrid in the RCCX module

Detection of the CYP21 deletion in congenital adrenal hyperplasia (CAH) in the RCCX module has been previously done by Southern blot analysis with multiple probes and separate digestions with the restriction endonucleases TaqI and BglII, which is laborious and indirect. Here, we describe an established PCR-based amplification method to analyze directly a CAH patient with a single CYP21 deletion, followed by RFLP analysis to characterize the interconversion region between tenascin A (TNXA) and tenascin B (TNXB). Data indicate that TaqI digestion of the defective CYP21 gene in the CAH patient produced 3.2-kb fragments. The CYP21 allele carried mutations in the CYP21P gene as determined by analysis with the amplification-created restriction site method. In addition, RFLP analysis indicated that the TNXB gene in the defective allele was replaced by TNXA to produce a TNXA/TNXB hybrid. We conclude that deletion of the RCCX module in this CAH patient included the RP2, C4B, and CYP21 genes and part of the TNXB gene. The junction of the recombination of the TNXA/TNXB hybrid may be located between IVS44 and exon 44 of the TNXB gene. This rapid, nonradioactive detection method will be beneficial for diagnostic purposes that are limited to the population originally studied.     

Identification of four novel mutations in the CYP21 gene in congenital adrenal hyperplasia in the Chinese

Congenital adrenal hyperplasia (CAH) is a common autosomal recessive disorder mainly caused by defects in the steroid 21-hydroxylase (CYP21) gene. We have analyzed CYP21 gene sequences in 65 CAH families in Taiwan. All ten exons of the CYP21 gene were analyzed by differential polymerase chain reaction followed by single-strand conformation polymorphism electrophoresis and the amplification-created restriction site method. About 95% (123 chromosomes) contain mutations due to conversion of DNA sequences into its neighboring homologous pseudogene, CYP21P. Four novel mutations representing 5% of the total chromosomes have also been identified. The mutations were confirmed by sequencing an aberrant DNA fragment. These four mutations included a base change of the splicing donor site at intron 2 from GT to AT, a base substitution of C to T at codon 316, deletion of ten bases (TCCAGCTCCC) at codons 330–333 of exon 8, and duplication of 16 bases (CCTGGATGACACGGTC) at codons 393–397 of exon 9. The loss of the splicing donor site at intron 2 and the premature stop at codon 316 may result in aberrant splicing to reduce enzyme activity and a truncated protein with no enzyme activity, respectively. Likewise, both the duplication and the deletion forms create a frameshift and premature stop during translation. The resulting proteins lack the heme-binding domain and hence are expected to lose enzymatic activity. Since these mutations are not found in the neighboring CYP21P pseudogene, gene conversion should not be the cause of these novel mutations. Received: 20 April 1998 / Accepted: 30 May 1998     

Population analysis of vitamin D receptor polymorphisms and the role of genetic ancestry in an admixed population

The vitamin D receptor (VDR) is an essential protein related to bone metabolism. Some VDR alleles are differentially distributed among ethnic populations and display variable patterns of linkage disequilibrium (LD). In this study, 200 unrelated Brazilians were genotyped using 21 VDR single nucleotide polymorphisms (SNPs) and 28 ancestry informative markers. The patterns of LD and haplotype distribution were compared among Brazilian and the HapMap populations of African (YRI), European (CEU) and Asian (JPT+CHB) origins. Conditional regression and haplotype-specific analysis were performed using estimates of individual genetic ancestry in Brazilians as a quantitative trait. Similar patterns of LD were observed in the 5' and 3' gene regions. However, the frequency distribution of haplotype blocks varied among populations. Conditional regression analysis identified haplotypes associated with European and Amerindian ancestry, but not with the proportion of African ancestry. Individual ancestry estimates were associated with VDR haplotypes. These findings reinforce the need to correct for population stratification when performing genetic association studies in admixed populations.     

C4A gene deletion and HLA associations in black Americans with systemic lupus erythematosus

In North America and European Caucasoids with systemic lupus erythematosus (SLE) there is an increased frequency of aC4A, CYP21A gene deletion, largely associated with theHLA-B8,DR3,C4A ^* QO extended haplotype. There have been no consistent HLA associations reported for SLE in blacks, although an increased frequency of serologically determinedC4A null alleles has been reported in two studies. We studied 79 black American SLE patients and 68 black controls by restriction fragment length polymorphism analysis to dermine if aC4A gene deletion was a genetic risk factor for SLE. Moreover, the nature of the deletion and any HLA phenotypic associations were sought. Nineteen of 79 (24%) patients compared to 5 of 68 (7.4%) controls had a phenotypicC4A,CYP21A gene deletion (P=.005; RR=4). A homozygous deletion in four patients gave a genotypic frequency of 23/158 (14.5%) SLE patients vs 5/136 (3.7%) controls (P=.001; RR=4.5). The deletion was associated with HLA-DR2 (P=.03) and HLA-DR3 (P=.03). Moreover, all subjects with the deletion had HLA-DR2 or DR3 (P=7.7×10⁻⁶). HLA-B44 was also associated with the deletion (P=.02), and eight of the nine HLA-B44 positives also carried HLA-DR2. HLA-B8 approached significance (P=.08) and was always accompanied by HLA-DR3. Finally, this black population demonstrated a uniqueC4B gene size polymorphism with 80% C4B “short” as compared to the 40% C4B “short” frequency reported in whites. We conclude that a largeC4A,CYP21A gene deletion, particularly associated with theHLA-B44,-DR2, and-DR3 alleles, is the strongest genetic risk factor thus far identified for SLE susceptibility in black Americans. Furthermore, the unique preponderance of theC4B “short” gene form may be a factor in the actual formation of the deletion.     

Isolation and characterization of polyhydroxyalkanoates inclusions and their associated proteins in Pseudomonas sp. 61-3

Two types of polyester inclusions of poly(3-hydroxybutyrate) [P(3HB)] and poly(3HB-co-3-hydroxyalkanoates) [P(3HB-co-3HA)] were isolated from crude extract of Pseudomonas sp. 61-3. Proteins associated with each inclusion were separated by SDS-PAGE. PHA synthase 1 (PhaC1(Ps)), PhaF(Ps), and PhaI(Ps) were identified from P(3HB-co-3HA) inclusions by N-terminal amino acid sequences analyses, as well as PHB synthase (PhbC(Ps)) and 24-kDa unknown protein were identified from P(3HB) inclusions. The structural genes of PhaF(Ps) and PhaI(Ps) were located downstream of the pha locus. The relative PHA/PHB synthase activities of each inclusion were measured for various 3-hydroxyacyl-coenzyme As of 4-12 carbon atoms. Direct atomic force microscopy observation of P(3HB) and P(3HB-co-3HA) inclusions demonstrated that the two types of inclusions had different morphologies.     

A case of first trimester prenatal diagnosis of 21-hydroxylase deficiency with human complement C4 cDNA probe

Early prenatal diagnosis of 21-hydroxylase (21-OHase) deficiency would enable treatment to be done to protect the fetus from masculinization and/or life-threatening adrenal crisis at birth. We report here the prenatal diagnosis of 21-OHase deficiency with human complement component C4 cDNA to probe DNA from chorionic villi at 10 weeks of gestation. Southern analysis with human C4 cDNA identified TaqI restriction fragment length polymorphisms (RFLPs) in the family. Family analysis with these RELPs showed that the fetus was not affected at greater than 99% probability, because the frequency of recombination between the 21-OHase B gene and the C4 gene would be extremely low.     

Diversity of the CYP21P-like gene in CYP21 deficiency

More than 90% of cases of congenital adrenal hyperplasia (CAH) are caused by mutations of the CYP21 gene. The occurrence of defective CYP21 genes, including 15 mutations, has been attributed to intergenic recombination of DNA sequences from CYP21P, and shows no influence on the RP1-C4A-CYP21P-XA-RP2-C4BCYP21- TNXB gene locus on chromosome 6p21.3. However, multiple gene deletions in this region produce at least three categories of gene arrangements: (a) C4A-CYP21P/CYP21-TNXB, in which there is a CYP21P/CYP21 fusion gene; (b) C4A-XCYP21-TNXB, where XCYP21 indicates that the CYP21 gene contains mutations of IVS2 (-12A/C>G and 707-714delGAGACTAC); and (c) C4A-CYP21P-TNXA/TNXB, in which the TNX A and B genes are fused. Among them, seven different structures of the CYP21 haplotype were found at these three loci. Formation of the C4A-CYP21P/CYP21-TNXB locus produced four distinct CYP21P/CYP21 chimeras. The C4A-XCYP21-TNXB locus contained the IVS2 mutation -12A/C>G and 707-714delGAGACTAC from the XCYP21 gene; and two kinds of TNXA/TNXB hybrids were found in the C4A-CYP21P-TNXA/TNXB locus. The seven different CYP21 alleles produced 3.2 kb Taq I fragments caused by deletion of the RP2-XA-C4B locus. Therefore, production of a 3.2-kb CYP21 allele shows diversity, but is not a unique feature of the CYP21P gene. Most of these gene arrangements probably exist in the C4A-XCYP21-TNXB and C4A-CYP21P/CYP21-TNXB gene loci. The existence of the C4A-CYP21P-TNXA/TNXB locus might not be common in CAH patients with 21-hydroxylase deficiency.     

广州地区106例汉族人群MICA和MICB微卫星基因座 单体型研究

利用聚合酶链反应和荧光（6－FAM）自动化检测技术对广东地区汉族106例无亲缘关系样本进行MICA基因外显子5和MICB基因内含子1微卫星基因座多态性及其单体型分布调查。根据群体资料估算两者间的单体型频率、连锁不平衡参数、相对连锁不平衡参数。结果显示,广州地区汉族人群MICA和MICB微卫星基因座基因型分布符合Hardy-Weinberg平衡法则,共检出MICA微卫星基因座 5个等位基因, MICB微卫星基因座14个等位基因。其中MICA A5基因频率最高（0.2877）,A4基因频率最低（0.1321）。MICB CA14等位基因频率最高（0.3255）,CA19、CA28等位基因频率最低（0.0047）,未检出CA27。21种MICA－MICB单体型频率大于1%(连锁不平衡参数>0), 其中单体型A5－CA14 (16.73%), A5.1－CA18 (8.75%), A4－CA26(3.76%),A9－CA15(3.66%)和A6－CA21(2.61%)为强连锁常见单体型（χ2>3.84, P<0.05）。广州地区汉族人群MICA和MICB微卫星基因座多态性和单体型分布有其自身特点,MICA和MICB微卫星基因座适合做为遗传标志,用于人类学、遗传疾病基因连锁分析、法医学亲子鉴定和个体识别等研究领域。Abstract: This study is to investigate genetic polymorphisms and haplotypes of microsatellite locus in the exon 5 of the MICA gene and intron 1 of the MICB gene based on 106 samples of Guangzhou Han Population by polymerase chain reaction and fluorescent technique (6-FAM). The corresponding haplotype frequencies, linkage disequilibria values and relative linkage disequilibria values were estimated based on population data. The results show that the genotype distributions of MICA and MICB microsatellite meet Hardy-Weinberg equilibrium in Guangdong Han population. In total, 5 alleles of MICA microsatellite locus and 14 alleles of MICB microsatellite locus were observed. MICA A5 was the most common allele (0.2877), whereas A4 was the least popular one (0.1321). MICB CA14 was the most common allele (0.3255), and CA19 and CA28 were the least popular ones (0.0047). CA27 was not observed. Twenty-one kinds of MICA-MICB haplotypes occurred at frequencies of more than 1% (linkage disequilibria value>0). The common MICA-MICB haplotypes were A5-CA14（16.73％）, A5.1- CA18 (8.75%), A4- CA26(3.76%),A9-CA15(3.66%) and A6-CA21(2.61%)（χ2>3.84, P<0.05）, and they were strong linkage disequilibria. The polymorphisms and haplotypes distributions of MICA and MICB microsatellite locus in Guangzhou Han population have their own genetic characteristics. The microsatellite locus of the exon5 of the MICA gene and intron 1 of the MICB gene could be used as the genetic markers in the studies of anthropology, linkage analysis of genetic disease genes, individual identification and paternity test in forensic medicine.