A novel gene encoding a B-box protein within the BRCA1 region at 17q21.1

A novel cDNA clone was isolated using a polyclonal serum directed against partially purified ovarian carcinoma antigen CA125. The deduced peptide sequence lacked membrane protein characteristics expected for CA125 but encompassed a B-box/coiled coil motif present in many genes with transformation potential. The gene was mapped by fluorescence in situ hybridization within the minimum region known to contain the familial breast/ovarian carcinoma gene, BRCA1. YAC and cosmid clones were isolated and used to refine the location of this gene adjacent and proximal to the RNU2 locus. The exon structure of the gene was determined. Extensive SSCP and sequence analysis of over 100 tumour and normal DNAs from familial and sporadic breast cancers and sporadic ovarian cancers failed to detect mutations in the coding region of this gene.

Acute promyelocytic leukaemia and the t(15;17) translocation

Acute promyelocytic leukaemia (APL) is a rare acute myeloid leukaemia characterized by a distinctive coagulopathy, the differentiation of promyelocytes in response to all-trans retinoic acid and a reciprocal chromosomal translocation, t(15;17)(q22;q12-q21). Molecular analysis of the APL breakpoint has revealed the involvement of the retinoic acid receptor alpha (RARA) gene on chromosome 17 and the promyelocytic leukaemia (PML) gene on chromosome 15. Both reciprocal fusion products which arise as a result of the translocation, PML/RAR alpha and RAR alpha/PML, are expressed in many patients. PML/RAR alpha, is implicated in leukaemogenesis, and may block myeloid differentiation directly and/or interfere with the normal function(s) of PML and/or RAR alpha.

Practice characteristics of graduates of postdoctoral general dentistry programs

A mail questionnaire was sent to 900 dentists who completed a Postdoctoral General Dentistry (PGD) program in 1985 and 900 dentists who graduated from dental school in 1985 but did not participate in a PGD program. The response rate was 57 percent. Three-quarters of the PGD graduates trained in civilian programs with the remainder being equally divided between military and Veterans Administration (VA) programs. Graduates of military programs continued to be employed by the military five years after graduation in contrast to the VA where less than 2 percent of graduates were employed after five years. The percent of dentists who are specialists or are enrolled in specialty programs five years after graduation was approximately 13 percent and the rates were similar for PGD and non-PGD dentists. The patterns of care in private practice tended to be similar for both groups; however, in institutions GPR graduates provided more treatment for special care patients and patients who were economically disadvantaged. GPR graduates also were more involved in teaching and in hospital activities.

Breast-feeding of very low birth weight infants

Twenty very low birth weight infants (birth weight < 1500 gm) were assessed to compare the clinical effects of breast and bottle feedings. The infants started breast-feeding during the same week that they started bottle feedings. Five breast-feedings and five bottle feedings for each infant were observed. Axillary temperature and weight before and after feedings were measured, and oxygen saturation, respiratory rate, and heart rate were monitored and recorded every 2 minutes during the feeding periods. The results showed no difference in oxygen saturation during breast-feeding (p = 0.056) but a lower incidence of oxygen desaturation (< 90%) (21% vs 38% in breast-feeding vs bottle feeding, respectively; p < 0.025). Infants with bronchopulmonary dysplasia had higher oxygen saturation during breast-feeding than during bottle feeding (p < 0.025), but weight gain during breast-feeding sessions was less (median, no gain vs 31 gm, p < 0.001). We conclude that (1) very low birth weight infants can tolerate both breast and bottle feedings at the same postnatal age; (2) very low birth weight infants are less likely to have oxygen desaturation to less than 90% during breast-feeding; and (3) weight gain is less during breast-feeding, probably because of lower intake, and may require more lactation counseling or supplementation of the feedings.

Molecular cloning and chromosomal localization to 17q21 of the human WNT3 gene

In mouse mammary tumors, the Wnt-3 gene can be activated by proviral insertion. Here we report on the isolation of a human homolog, WNT3. A genomic clone was isolated by use of mouse Wnt-3 sequences as a probe, after which cDNA containing most of the protein-encoding domain of the human gene was obtained by PCR. Comparison between the deduced mouse and human WNT-3 protein sequences showed four changes in 333 amino acids. WNT3 is located on chromosome 17q21. The gene was not found to be amplified or rearranged in a collection of human breast tumors.

Localization of a second NM23 gene, NME2, to chromosome 17q21-q22

NM23 is a candidate tumor suppressor protein and has recently been identified as an NDP kinase. The expression of NM23 is inversely related to the metastatic potential of tumor cells. Two NM23 genes, NME1 and NME2, that code for the A and B chains of the kinase, respectively, have been cloned. To determine the human chromosomal location of the NME2 gene, we have analyzed DNA from rodent-human cell lines and hybrid cell lines containing portions of chromosome 17 by a combination of PCR amplification and Southern hybridization. The NME2 gene was mapped to the chromosome region 17q21-q22, the same region in which the NME1 gene has been localized. This region is linked to the early onset breast/ovarian locus (BRCA1) and allelic deletions of NME1 have been associated with metastatic potential of colorectal carcinomas.

Localization of the retinoid X receptor alpha gene (RXRA) to chromosome 9q34

The retinoid X receptor alpha is one of a number of retinoic acid receptors which are members of the steroid/thyroid hormone superfamily. Localization of RXRA was achieved using the polymerase chain reaction on a panel of somatic cell hybrids. A cosmid clone was isolated using the RXRA PCR product, and this was used to further localize the gene by fluorescence in situ hybridization to chromosome 9q34 distal to the dopamine beta hydroxylase gene (DBH). This mapping position was confirmed by PCR on a panel of translocation hybrids.

A long-range restriction map of human chromosome 5q21-q23

A long-range restriction map encompassing the APC (adenomatous polyposis coli) gene has been constructed. The map includes 35 DNA markers and consists of two segments of 10 and 2.5 Mb. Published genetic markers have been connected using additional, nonpolymorphic DNA probes. The map clarifies marker order and allows comparison of physical and genetic data.

Very frequent loss of heterozygosity throughout chromosome 17 in sporadic ovarian carcinoma

Frequent loss of heterozygosity (LOH) on both arms of chromosome 17 has been described in ovarian carcinoma (OC) by a number of groups, and the recent fine mapping of an inherited breast-ovarian cancer gene (brcAI) to a small region at 17q12-21 has focused interest on this area. We studied 28 sporadic OCs with 21 markers at 18 loci on chromosome 17 (5 on 17p and 13 on 17q). LOH on 17p was 78%, and always involved p53. In 86% of cases showing LOH, all informative markers on chromosome 17 showed reduction to homozygosity. Using 6 markers flanking the brcAI locus on 17q, LOH was 75%, but only one tumour showed LOH with telomeric retention. The data therefore suggest that small deletions on chromosome 17 are very uncommon in sporadic OC. No genomic rearrangements by Southern blotting were seen in the brcAI candidate gene estradiol 17 beta dehydrogenase 2 (17hsd2), or in erbB2, prohibition (phb) and nmeI (previously nm23-HI). LOH on chromosome 17 was more common in high-grade, late-stage carcinomas, and no LOH was seen in any benign or borderline tumour. This study has clearly demonstrated that LOH at any one site on chromosome 17 is most commonly explained by LOH over the whole of the chromosome. We consider possible reasons for the absence of small deletions on chromosome 17 in OC.

THRA1 and D17S183 flank an interval of < 4 cM for the breast-ovarian cancer gene (BRCA1) on chromosome 17q21

In order to pinpoint the locale of the gene for early-onset familial breast and ovarian cancer (BRCA1), polymorphisms were developed within the locus for thyroid hormone receptor alpha (THRA1) and for several anonymous sequences at chromosome 17q12-q21. The THRA1 polymorphism is a dinucleotide repeat with 10 alleles and heterozygosity.79. Gene mapping in extended families with inherited, early-onset breast and ovarian cancer indicates that BRCA1 is distal to THRA1 and proximal to D17S183 (SCG43), an interval of < 4 cM. This locale excludes HER2, THRA1, WNT3, HOX2, NGFR, PHB, COLIA1, NME1, and NME2 as candidates for BRCA1 but does not exclude RARA or EDH17B. Resolving the remaining recombination events in these families by new polymorphisms in the THRA1-D17S183 interval will facilitate positional cloning of the breast-ovarian cancer gene on chromosome 17q12-q21.

Linkage analysis of early-onset breast and ovarian cancer families, with markers on the long arm of chromosome 17

We have conducted linkage analysis in 16 breast cancer families, 13 of which are classified as site-specific breast cancer families and 3 of which are classified as breast-ovary families. Linkage analysis has largely focused on a single extended breast-ovary family. Analysis of all families combined shows significant evidence for linkage to 17q (LOD = 3.63 at theta = .0, for linkage to NME1), confirming the observations of Hall et al. and Narod et al. Many families were consistent with linkage, but their limited size and informativeness precluded confirmation of linkage. A putative recombinant in a breast-ovary family suggests that BRCA1 is distal to D17S250.

A somatic cell hybrid map of the long arm of human chromosome 17, containing the familial breast cancer locus (BRCA1)

We describe a detailed somatic cell hybrid map of human chromosome 17q11.2-q23, containing the familial breast and ovarian cancer locus (BRCA1) and highly informative closely linked markers. An X-irradiation panel of 38 hamster/human and mouse/human hybrids with fragments of chromosome 17 was generated and characterized with 22 STS markers from this chromosome. A detailed map of 61 probes onto chromosome 17q, subdividing the chromosome arm into 25 regions, was done by using a panel of hybrids with well-defined breakpoints and nine chromosome-mediated gene transfectants. Our localization of RARA, TOP2, EDH17B1 and 2, and possibly WNT3, between THRA1 and D17S181, two markers known to flank BRCA1, suggests that any of these is a potential candidate for the BRCA1 locus. The marker D17S579 (Mfd188), which is believed to be very close to BRCA1, maps closest to the EDH17B genes.

The search for the familial breast/ovarian cancer gene

Familial breast cancer is a very common autosomal dominant disorder in women. A predisposing gene for breast and ovarian cancer (BRCA1) has been mapped by linkage analysis to the long arm of chromosome 17. In almost all families with breast and ovarian cancer and half of those with only breast cancer, the disease is linked to this gene. The BRCA1 gene, which is also believed to be involved in sporadic breast and ovarian cancer, should soon be identified.

Molecular analysis of the t(15;17) translocation in acute promyelocytic leukaemia

APL (FAB M3) is a unique type of myeloid leukaemia characterized by specific clinical, morphological, cytogenetic and molecular features. An early and accurate diagnosis is necessary to initiate therapy and treat the life-threatening coagulopathy caused by release of procoagulants from the abundant promyelocytic granules. Cytogenetically the disease is characterized by a reciprocal translocation between the long arms of chromosomes 15 and 17, t(15;17)(q21;q22), which is seen in almost every patient with APL but in no other form of malignancy. The presence of this translocation, often as the only karyotypic change, suggests that potentially leukaemogenic sequences are located at the breakpoints and are activated by rearrangement. The recent cloning of the breakpoints by three groups has demonstrated that the retinoic acid receptor alpha gene (RARA) on chromosome 17 is fused to a previously undescribed transcription factor gene, PML, on chromosome 15. The DNA-binding motifs of both the RARA and PML proteins, together with the ligand-binding domain of RARA, are combined in a single fusion protein which may dysregulate either retinoic acid or PML-sensitive pathways. Identification of these dysregulated target genes has become the next molecular goal for research on APL. Intriguingly, some APLs not only express the PML-RARA fusion protein but also the reciprocal RARA-PML fusion protein, although the contribution of this product is unclear. The PML-RARA chimaeric protein is presumably the target during the striking differentiation therapy achieved with all-trans retinoic acid. This therapy induces the malignant promyelocytes to mature and die, rather than continue proliferating. Moreover, it represents the first direct connection between a genetic defect and clinical treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Yeast artificial chromosomes for the molecular analysis of the familial polyposis APC gene region

Two yeast artificial chromosomes (YACs) spanning a total distance of 1.1 megabase pairs of DNA around the MCC (for mutated in colorectal carcinoma) and APC (for adenomatous polyposis coli) genes at 5q21 have been isolated and characterized. Starting from the MCC gene, a strategy was undertaken to identify constitutional submicroscopic deletions in familial adenomatous polyposis patients that might considerably narrow down the position of the APC gene. To this end, YACs identified by the MCC gene were screened across a chromosome 5-specific cosmid library to provide a source of DNA probes for genomic scanning. The cosmids isolated from these experiments were used to screen a panel of somatic cell hybrids containing chromosome 5 segregated from patients suspected to carry putative interstitial deletions. This screening approach led to the confirmation of a small heterozygous deletion in a polyposis patient that overlaps one of the two isolated YACs. This YAC has been shown to contain the entire APC gene, in addition to a significant portion of DNA flanking the 5' end of the gene, and should therefore prove a valuable resource for functional studies by transfer to colorectal tumor-derived cell lines.

Genetic heterogeneity of early-onset familial breast cancer

A gene for early-onset familial breast cancer has recently been mapped to the chromosome 17q12-23 region. In order to confirm the gene location, we have tested an extensive early-onset breast cancer family with 4 markers in this chromosome region. Linkage was negative with all 4 markers. This study suggests that there is genetic heterogeneity among early-onset breast cancer families.

Hypertrophic cardiomyopathy associated with dexamethasone therapy for bronchopulmonary dysplasia

The potential induction of cardiac effects by high-dose dexamethasone therapy was evaluated prospectively in 13 respirator-dependent infants with bronchopulmonary dysplasia by means of two-dimensional and M-mode echocardiography. The initial divided dose of dexamethasone was 500 micrograms/kg per day, tapered progressively for as long as 6 weeks. Evaluations were made before treatment and at 3, 7, 14, 21, 28, 35, and 42 days after the start of dexamethasone therapy. This regimen was associated with a significant (p less than 0.01) increase in thickness of the interventricular septum (2.60 +/- 0.09 to 4.00 +/- 0.16 mm), diastolic left ventricular free wall (2.80 +/- 0.13 to 4.06 +/- 0.20 mm), and diastolic right ventricular free wall (1.55 +/- 0.08 to 2.02 +/- 0.12 mm). In addition, seven dexamethasone-treated infants but no control infants had systolic anterior motion of the mitral valve (p less than 0.001). These effects were transient, reached their maximal degree by the third week of treatment, and approached pretreatment conditions by the sixth week of treatment. Ejection fraction was not affected; heart rate and mean arterial pressure were transiently increased during dexamethasone therapy. We conclude that a transient absolute myocardial hypertrophy is associated with dexamethasone therapy in infants with bronchopulmonary dysplasia. The mechanism or mechanisms through which this hypertrophy arises and the cardiopulmonary implications are unclear.

The NM23 gene maps to human chromosome band 17q22 and shows a restriction fragment length polymorphism with BglII

The NM23-Hl gene is a putative tumor suppressor gene that may be important in the metastasic process. Recent genetic and immunological data indicate that the NM23-Hl gene encodes a protein with nucleoside diphosphate (NDP) kinase activity. The mapping of NM23-Hl by panels of rodent-human somatic cell hybrids and in situ hybridization showed that the gene is located in human chromosome band 17q22. A two-allele polymorphism with BglII was demonstrated.

Assignment of apolipoprotein H (APOH: beta-2-glycoprotein I) to human chromosome 17q23----qter; determination of the major expression site

Human apolipoprotein H (APOH) is associated with lipoprotein present in plasma. It has been shown that APOH has structural similarities with the regulation of complement activation (RCA) protein superfamily and is involved in phospholipid binding interactions on platelets and as an autoantigen in complex with anionic phospholipids. Nevertheless, additional functional studies are necessary to establish the physiological role of APOH. By hybridizing a cDNA probe for APOH to a panel of somatic cell hybrids, we show that the structural locus for this protein maps to 17q23----qter and is therefore not part of the RCA cluster on chromosome 1. The site of biosynthesis for APOH was established by Northern blot analysis. Hybridization of the APOH cDNA probe to total liver RNA identified a transcript of approximately 1.5 kb.

The human collagen X gene. Complete primary translated sequence and chromosomal localization

We report on the complete primary translated sequence of human alpha 1(X) collagen, deduced from a genomic clone, and the chromosomal localization of the human collagen X gene. The primary translated product of human collagen X is encoded by two exons of 169 bp and approx. 2940 bp. The 169 bp exon encodes 15 bp of 5'-end untranslated sequence, 18 amino acid residues (54 bp) of signal peptide and 33 1/3 amino acid residues (100 bp) of the N-terminal non-collagenous domain. The 2940 bp exon encodes 4 2/3 amino acid residues (14 bp) of the N-terminal non-collagenous domain, the complete triple-helical domain of 463 amino acid residues (1389 bp), the complete C-terminal non-collagenous domain of 161 amino acid residues (483 bp) and 1054 bp of 3'-end untranslated sequence up to and including a potential cleavage/polyadenylation signal. The size of the intron separating the two exons, as estimated by partial sequencing and Southern-blot analyses, is approx. 3200 bp. By a combination of somatic cell hybrid screening and hybridization in situ the human collagen X gene (COL10A1) has been assigned to the distal end of the long arm of chromosome 6 at the locus 6q21-6q22.3.