David J. Munroe

A novel moesin-, ezrin-, radixin-like gene is a candidate for the neurofibromatosis 2 tumor suppressor

Neurofibromatosis 2 (NF2) is a dominantly inherited disorder characterized by the occurrence of bilateral vestibular schwannomas and other central nervous system tumors including multiple meningiomas. Genetic linkage studies and investigations of both sporadic and familial tumors suggest that NF2 is caused by inactivation of a tumor suppressor gene in chromosome 22q12. We have identified a candidate gene for the NF2 tumor suppressor that has suffered nonoverlapping deletions in DNA from two independent NF2 families and alterations in meningiomas from two unrelated NF2 patients. The candidate gene encodes a 587 amino acid protein with striking similarity to several members of a family of proteins proposed to link cytoskeletal components with proteins in the cell membrane. The NF2 gene may therefore constitute a novel class of tumor suppressor gene.

Mapping of ribosomal protein S3 and internally nested snoRNA U15A gene to human chromosome 11q13.3–q13.5

The mammalian ribosome is a massive structure composed of 4 RNA species and about 80 different proteins. One of these ribosomal proteins, S3, appears to function not only in translation but also as an endonuclease in repair of UV-induced DNA damage. Moreover, the first intron of human RPS3 transcripts is processed to generate U15A, a small nucleolar RNA. We localized the nested RPS3/U15A genes to the immediate vicinity of D11S356 and D11S533 on human chromosome 11q13.3-q13.5 using a combination of somatic cell hybrid analysis, fluorescence in situ hybridization, and YAC/STS content mapping. These findings add to the evidence that genes encoding ribosomal proteins are scattered about the human genome.

Single-strand conformational polymorphism (SSCP) mapping of the mouse genome: integration of the SSCP, microsatellite, and gene maps of mouse chromosome 1.

Interspersed repetitive sequence (IRS) PCR and repetitive element-to-bubble (IRS-bubble) PCR have been utilized to rapidly generate large numbers of mouse-specific, chromosome 1-enriched STSs from mouse-hamster somatic cell hybrids. Single-strand conformational polymorphism (SSCP) has been used to localize 39 new repetitive element-linked STSs to the mouse map: 22 to Chr 1, 10 to Chr. 15, 2 each to Chrs 12 and 14, and three to Chr 7. In addition, we have integrated the SSCP, single-strand length polymorphism, and restriction fragment length polymorphism maps of mouse Chr. 1, resulting in a high-density map of the chromosome, containing over 100 loci, all typed on a single interspecific backcross.

Chromosomal Localization of 15 Ion Channel Genes

Several human Mendelian diseases, including the long-QT syndrome, malignant hyperthermia, and episodic ataxia/myokymia syndrome, have recently been demonstrated to be due to mutations in ion channel genes. Systematic mapping of ion channel genes may therefore reveal candidates for other heritable disorders. In this study, the GenBank and dbEST databases were used to identify members of several ion channel families (voltage-gated calcium and sodium cardiac chloride, and all classes of potassium channels). Genes and ESTs without prior map localization were identified based on GDB and OWL database information and 15 genes and ESTs were selected for mapping. Of these 15, only the serotonin receptor 5HT3R had been previously mapped to a chromosome. A somatic cell hybrid panel (SCH) was screened with an STS from each gene and, if necessary, the results verified by a second SCH panel. For three ESTs, rodent derived PCR products of the same size as the human STS precluded SCH mapping. For these three, human Pl clones were isolated and the genomic location was determined by metaphase FISH. These genes and ESTs can now be further evaluated as candidate genes for inherited cardiac, neuromuscular, and psychiatric disorders mapped to these chromosomes. Furthermore, the ESTs developed in this study can be used to isolate genomic clones, enabling the determination of each transcripts genomic structure and physical map location. This approach may also be applicable to other gene families and may aid in the identification of candidate genes for groups of related heritable disorders.

407-2 Characterization of a Recombination Event Excluding the Harvey-ras-1 (H-ras-1) Locus in a Romano-Ward Long QT Syndrome Family Linked to Chromosome 11p15 and Isolation of a Polymorphic Repeat Telomeric to H-ras-1

The Romano-Ward Long QT Syndrome (RWLQTS) has been linked to chromosome 11 p15.5 in several large families but demonstrates genetic heterogeniety. To date, there has been no published recombination between the Harvey- ras -1 (H- ras -1) locus and the RWLQTS in families linked to 11p15. The one LOD confidence interval for the RWLQTS gene is 3 cM from H- ras -1 (Keating et al, 1992). In a large multigenerational family, we demonstrate linkage of the RWLQTS to marker D11S932 on 11p15 with a LOD score of 3.14 at a theta of 0. The family was genotyped for the following 11p markers: H- ras -1 (2 markers), insulin growth factor II, tyrosine hydroxylase(TH), β-hemoglobin, D11S860, D11-S1363, D11S902, D11S1318, D11S1331, D11 S1323, D11S1338, D11S909, D11S932, and Dl1S922. An unaffected individual and her two unaffected offspring carry the affected haplo-type for the H- ras -1 region, spanning from H- ras -1 to TH. All three individuals had a QTc ≤ 0.40 seconds and no history of syncope making the diagnosis of RWLQTS extremely unlikely. This suggests that, although the gene for the RWLQTS is linked to chromosome 11 p15 in this family, a recombination event may have occurred that separated the RWLQTS gene from the affected H- ras -1 region haplotype, Multipoint analysis indicates the most likely location for the RWLQTS gene in this family is near D11S932. To investigate a possible telomeric recombination event, cosmids telomeric to H- ras -1 were isolated. From one of these cosmids, a CA/CT repeat marker (78% heterozygosity) was characterized and its location telomeric to H- ras -1 was verified by interphase FISH. Genotyping of the family demonstrated that the same three unaffected individuals had the affected allele for this marker as well. However, due to the genotypes in the family, we could not exclude a telomeric recombination event. Based on its degree of heterozygosity, this marker will be extremely useful in the physical and genetic mapping of the 11 p telomere. The recombination event in this family should aid the localization of the RWLQTS gene linked to chromosome 11 p15. This is the first report of recombination between the H- ras -1 locus and the RWLQTS phenotype in a family in which RWLQTS is linked to 11 p15.