D.F. Callen

Localization of the human multiple drug resistance gene, MDR1, to 7q21.1

SummaryMultiple drug resistance has been shown to be associated with amplification/increased expression of a gene designated MDR. The localization of one member of the MDR gene family, MDR1, to the long arm of chromosome 7 by in situ hybridization is reported.

Isolation and characterisation of (AC)n microsatellite genetic markers from human chromosome 16

A cosmid library of human chromosome 16 has been subcloned, and (AC)n microsatellite positive clones have been identified and sequenced. Oligonucleotide primers flanking the repeat were designed and synthesized for (AC)n microsatellites with n greater than 16. These microsatellite loci were then mapped by PCR using a somatic cell hybrid panel of human chromosome 16, and their heterozygosities and allele frequencies determined. Fourteen (AC)n microsatellites were mapped to discrete physical intervals of human chromosome 16 defined by a mouse/human hybrid panel. Nine of these have expected heterozygosities ranging between 0.60 and 0.79, four have expected heterozygosities between 0.02 and 0.49, and one detected three loci where the alleles could not be resolved.

Human chemokines fractalkine (SCYD1), MDC (SCYA22) and TARC (SCYA17) are clustered on chromosome 16q13.

Chemokines are a large family of small secreted proteins that regulate migration of white blood cells. Based on the arrangement of the first two of the four conserved cysteine residues, chemokines are classified into four subfamilies, CXC, CC, C and recently identified CX3C. Most of the human genes for the CC chemokines are clustered at chromosome 17q11.2 (Naruse et al., 1996). Previously we identified a novel CC chemokine TARC (thymus and activation-regulated chemokine) (Imai et al., 1996) and localized its gene (SCYA17) at chromosome 16q13 (Nomiyama et al., 1996). Recently, Bazan et al. (1997) and Pan et al. (1997) mapped the CX3C chemokine fractalkine/neurotactin gene (SCYD1) to chromosome 16. More recently, Godiska et al. (1997) reported isolation of a cDNA encoding a novel CC chemokine MDC (macrophage derived chemokine) and mapped its gene (SCYA22) to the same chromosome. It is therefore important to determine the exact relationship of these three chemokine genes on chromosome 16. Materials and methods

Chromosomal assignment of the human deoxyribonuclease I gene, DNASE1 (DNL1), to band 16p13.3 using the polymerase chain reaction

To localize the human deoxyribonuclease I (DNase I) gene, DNASE1 (DNL1), we performed a polymerase chain reaction (PCR) using DNA extracted from a panel of cloned human x rodent hybrid cell lines carrying different human chromosomes and screened for the presence of the expected PCR products. Two different sets of oligonucleotide primers specific for human DNase I cDNA sequences were used to amplify unique fragments in the human DNase I gene. Based on this work, DNL1 could be assigned to human chromosome 16. Furthermore, regional localization of the gene to 16p13.3 was performed by PCR analysis of a high-resolution mouse x human somatic cell hybrid panel that contained defined portions of human chromosome 16.

Chromosomal location of the human tumor necrosis factor receptor genes

TNFR1 and TNFR2, the genes encoding the two forms of the human tumor necrosis factor receptor, were localized to normal human chromosomes by in situ hybridization and Southern blot analysis of a series of human x mouse hybrid cell lines. TNFR1 maps to 12p13 and TNFR2 maps to 1p36.

Fine mapping of gene probes and anonymous DNA fragments to the long arm of chromosome 16

The fragile site, FRA16B, at 16q22.100 and four different translocations with breakpoints at 16q22.102, 16q22.105, 16q22.108, and 16q22.3 were used to locate and order DNA probes. This was achieved by Southern analysis of a somatic cell hybrid panel containing portions of chromosome 16 and by in situ hybridization. The anonymous DNA fragments D16S6, D16S10, and D16S11 were proximal to FRA16B and located at 16q13----q22.100. D16S4 and LCAT were located at 16q22.100----q22.102. TAT and HP were located at 16q22.105----q22.108. CTRB was located distal to 16q22.105 and therefore is in the distal half of 16q22. The order of markers in this region was determined as centromere-D16S6, D16S11, D16S10, MT-FRA16B-D16S4, LCAT-HP,TAT,CTRB-APRT- telomere. Linkage studies to determine map distances between the closest markers flanking the fragile site are now in progress.

A new location for the human adenine phosphoribosyltransferase gene (APRT) distal to the haptoglobin (HP) and fra(16)(q23) (FRA16D) loci

The human adenine phosphoribosyltransferase gene (APRT) was mapped with respect to the haptoglobin gene (HP) and the fragile site at 16q23.2 (FRA16D). A subclone of APRT and a cDNA clone of HP were used for molecular hybridization to DNA from mouse-human hybrid cell lines containing specific chromosome 16 translocations. The APRT subclone was used for in situ hybridization to chromosomes expressing FRA16D. APRT was found to be distal to HP and FRA16D and was localized at 16q24, making the gene order cen-FRA16B-HP-FRA16D-APRT-qter.

The gene for human interleukin 7 (IL7) is at 8q12-13

SummaryThe gene for human interleukin 7 (IL7) maps to chromosome 8 by Southern analysis of a somatic cell hybrid panel and to 8q12-q13 by in situ hybridization.

High resolution characterization of an interstitial deletion of less than 1.9 Mb at 4p16.3 associated with Wolf-Hirschhorn syndrome.

Wolf-Hirschhorn syndrome (WHS) caused by 4p16.3 deletions comprises growth and mental retardation, distinct facial appearance and seizures. This study characterized a subtle interstitial deletion of 4p16.3 in a girl with mild retardation and possessing facial traits characteristic of WHS. The patient had generalized seizures in conjunction with fever at 3 and 5 years of age. Fluorescence in situ hybridization (FISH) with a series of markers in the 4p16.3 region showed that the interstitial deletion in this patient was between the probes D4S96 and D4S182, enabling the size of the deletion to be estimated as less than 1.9 Mb. This is the smallest interstitial deletion of 4p16.3 which has been reported. The patient contributes to a refinement of the phenotypic map of the WHS region in 4p16.3. The critical region for the characteristic facial changes of WHS, failure to thrive and developmental delay is now localized to a region of less than 700 kb. The mental retardation of this patient was mild suggesting that small interstitial deletion may have less severe phenotypic consequences.

Mapping the short arm of human chromosome 16

Physical mapping of 13 different breakpoints on the short arm of chromosome 16 using previously mapped probes and the subsequent mapping of additional probes enabled the division of this portion of the chromosome into six different intervals. D16S94 was mapped between HBA and D16S80 and is closer to PKD1 than either HBA or D16S80. A tight linkage group which includes FRA16A, D16S8, and D16S79 was identified. Seven breakpoints, including FRA16A, could not be separated by probe localizations. This study provides the basis for the development of detailed maps of the short arm of chromosome 16.