Genetic mapping of genes regulating the thymus size in back-cross rats between the laboratory BUF/Mna strain and the MITE strain derived from the wild rat, Rattus norvegicus

The thymoma prone BUF/Mna (B) rat is a useful model for Studying the genes responsible for thymus enlargement during the stage of young growth. Among the strains of rats, B rats have the largest thymuses at al stages of life. A locus, Ten-1 , which contributes to thymus enlargement in back-cross (BC) rats between the B and WKY/NCrj (W) strains, was mapped on chromosome 1. To determine the precise location of the bus, (B×(B×MITE)F1) BC rats were generated by crossing the B strain with the Inbred MITE (M) strain, which was established from captured, Japanese wild rats, and were examined by linkage study using polymerase chain reaction with 67 microsatellite markers. Linkages with thymus enlargements were found In genotypes of seven markers, BSIS, LSN, MYL2, IGF2, PBPC2, D1Mgh11 , and D1Mit6 , by X^2-test and Student's t -test, which confirmed the presence of the genetic locus associated with thymus enlargement, Ten-1 , in this region. Paradoxically, a suppressive locus, Tsu-1 , to thymus enlargement was also found on chromosome 3, showing linkages of phenotype of the small thymus with genotypes of SCN2A, CAT D3Mit16 , and D3Mit13 . By analyses of mapmaker/exp and mapmaker/qtl, Ten-1 was mapped at 4.6 cM proximal from IGF2 locus on chromosome 1 and Tsu-1 at 4.0 cM proximal from CAT locus on chromosome 3, respectively.     

Identification of three new DRB3* (DRB3*0106, DRB3*0107 and DRB3*02022) alleles

Three novel DRB3* alleles were identified using CANTYPE reverse hybridization assay. The initial unusual hybridization patterns of DRB3-specific polymerase chain reaction (PCR)-amplified DNA from each subject were confirmed by cloning and sequencing analysis. DRB3*0106 allele is identical to DRB3*0101 except for a single nucleotide substitution (CTG-->GTG) changing codon 38 from Leu to Val. This polymorphism is commonly found in DRB3*03 alleles. Compared with DRB3*0202, DRB3*02022 contains a single silent nucleotide substitution (AAT-->AAC, both encoding for Asn) at codon 77. This polymorphism is also present in DRB3*0204 allele. The new DRB3*0107 allele has a sequence unique to DRB3 alleles. From codon 5 to codon 36 the sequence is identical to that of DRB3*0101 allele. From codon 37 to codon 87 the sequence of DRB1*0107 allele is identical to that of DRB3*0202. This sequence would thus explain the CANTYPE(R) DRB3-specific unusual pattern of reactions. The new DRB3*0107 could have arisen from a gene conversion between DRB3*0101 and DRB3*0202 alleles, but the DRB3*0106 and the DRB3*02022 may have been generated by a point mutation event. The DRB3*0107 allele was identified in a Caucasoid individual. The ethnic origin of the subjects carrying the other two alleles are unknown. The three alleles presented here were only identified once, in a total population of 49,000.     

21－羟化酶CYP21B基因Ile~（172）→Asn错义突变

为了解先天性肾上腺皮质增生症患者的２１－羟化酶ＣＹＰ２１Ｂ基因中Ｉｌｅ~（１７２）→Ａｓｎ错义突变的发生率，根据放大受阻突变体系（Ａｍｐｌｉｆｉｃａｔｉｏｎｒｅｆｒａｃｔｏｒｙｍｕｔａｔｉｏｎｓｙｓｔｅｍ，ＡＲＭＳ）的要求，设计了３种引物：５＇ｄ（ＴＴＧＧＧＡＧＡＣＴＡＣＴＣＣＣＴＧＣＴＣＴ）３＇（共同引物）、５＇ｄ（ＡＧＧＴＧＡＧＧＴＡＡＣＡＧＡ）３＇（正常引物）、５＇ｄ（ＡＧＧＴＧＡＧＧＴＡＡＣＡＧＴ）３＇（突变引物），在７例患儿中进行了检测，发现具有本突变者３例。对其中一例进行的家系分析，结果提示：这组引物有快速、简便的优点，不需使用同位素就能对具有Ｉｌｅ~（１７２）→Ａｓｎ变异的高危家庭成员作产前诊断。     

Differential RNA fingerprinting as a tool in the analysis of spermatozoal gene expression

The apparent decline in human male fertility and the concomitantincrease in testicular pathology have prompted discussion ofthe underlying molecular mechanisms which may underpin theseobservations. While monitoring the expression of protamlne-2genes in the human ejaculate, we found a representative complementof sperm mRNAs following sequence-independent amplificationof reverse-transcribed cDNAs with the polymerase chain reaction(RT-PCR). The revelation of unique sperm-derived PCR productsusing this method suggests that it should now be possible toinvestigate gene expression in human spermatogenesis by differentialRNA fingerprinting of ejaculate spermatozoa. The Identificationof molecular markers and the corresponding genes associatedwith male Infertility will be considerably enhanced by theseinvestigations while obviating the requirement for invasivebiopsy.     

Use of HLA marker associations and HLA haplotype linkage to estimate disease risks in families with gluten-sensitive enteropathy

Based on a two-locus, double recessive model, we derive formulas for the risks that relatives of individuals with gluten-sensitive enteropathy (GSE) will also develop the disease. The calculations take advantage of: the linkage between the HLA locus and one of the two proposed GSE loci, and the preferential association of the HLA-DR3 and DR7 alleles with the GSE disease allele that occupies the HLA-linked locus. We use Bayes' rule to quantitate the strength of the association between the GSE disease allele and the HLA marker allele. This method predicts that siblings of the proband have an overall 10% risk for GSE, which is consistent with observed family data. This predicted risk rises to 30% when siblings are HLA-identical to the proband (also consistent with observed data) or when the sibling has the DR3 allele in the HLA haplotypes not shared with the proband. In those populations where DR7 also is associated with GSE, siblings of probands have a 10% predicted risk for GSE when only one HLA haplotype is shared with the proband and DR7 is included in the unshared haplotype. Other DR alleles are associated with much lower disease risks. By separating individuals into high and low risk groups, HLA typing identifies those individuals who would benefit from further diagnostic procedures. This general strategy should be applicable to other multilocus, marker-associated diseases.     

Precise mapping of the EGF receptor gene on the human chromosome 7p12 using an improved fish technique

Summary The gene for epidermal growth factor receptor (EGFR) has been localized to the p14-p12 region of human chromosome 7 by somatic cell hybridization and radioisotopein situ hybridization techniques. In this paper, we report the precise mapping of the EGFR gene to the band p12 of chromosome 7 using a novel method in which fluorescence images fromin situ hybridization and Q-banding are computer graphically merged. The novel procedure is described in detail.     

High incidence of the Cys 282 Tyr mutation in the HFE gene in the Irish population -implications for haemochromatosis

Abstract: A simple PCR-SSOP approach based on a single PCR product has been developed to screen the HFE gene for the haemochromatosis-associated mutations Cys 282 Tyr and His 63 Asp. Using this approach the prevalence of these mutations in a cohort (30) of haemochromatosis patients and normal controls (404) was determined. Ninety percent of the haemochromatosis patients were homozygous for the Cys 282 Tyr mutation. In the normal population we found an increased incidence of the Cys 282 Tyr mutation (17.3%; 95% confidence limits 0.136–0.209) which was also reflected in the higher frequency of Cys 282 Tyr homozygotes (1.24%; 95% confidence limits 0.0015–0.0232). Linkage disequilbrium analysis confirmed the association between A*03 and Cys 282 Tyr. However, strong linkage disequilibrium occurred with the HLA-A*03-associated allele HLA-B*14 but not the HLA-A*03-associated allele HLA-B*07. The His 63 Asp was found to be in linkage disquilibrium with HLA-A*29.     

HLA-DPB1 typing by polymerase chain reaction amplification with sequence-specific primers

DPB1 is the second most polymorphic class II locus with currently 84 recognized alleles, i.e. DPB1*0101 to DPB1*8101. Most of the alleles have been described during the last few years using oligonucleotide and sequencing techniques and relatively little is known about the role and importance of the polymorphic residues as regards to the function of DP molecules. In the present study, polymerase chain reaction (PCR) primers were designed for identification of all the phenotypically different DPB1 alleles by PCR amplification with sequence-specific primers. Forty-eight standard genomic PCR reactions per sample were performed in order to achieve this resolution. Unique amplification patterns were obtained in 2983 of 3160 (94.4%) possible genotypes. The primers were combined so that only very rare genotypes gave rise to ambiguous patterns. Sixty-four Histocompatibility Workshop cell lines and 150 DNAs provided by the UCLA DNA exchange were investigated by the DPB1 primer set. All typing results were conclusive. Analysis of the distribution of DPB1 alleles was performed in 200 Caucasian samples, 100 African samples and 40 Oriental samples. The population study by the DPB1 PCR-SSP method showed a characteristic distribution of HLA-DPB1 alleles. Each ethnic group had one, or two, frequent DPB1 allele(s) and the frequency of homozygotes was high, suggesting that balancing selection does not appear to be affecting the evolution of the DPB1 locus.