Efficiency of various strategies and materials to generate new markers: saturating the region 5q11.2-q13.3 with 30 new randomly distributed clones.

Several different strategies and materials were used for saturating the region 5q11.2-q13.3 with new, randomly distributed markers: isolation of human clones from three chromosome-5-specific libraries (a BssHII endclone phage library from the somatic cell hybrid H64 and two total genomic phage libraries from radiation hybrids IH12 and IH132), as well as Alu-PCR from chromosome-5-specific radiation hybrids with overlapping fragments in the region around the spinal muscular atrophy locus, followed either by direct isolation of Alu-PCR products or hybridization of Alu-PCR products to chromosome-5-gridded cosmid libraries. 253 human phage and cosmid clones were mapped to various parts of chromosome 5 by deletion mapping to somatic cell hybrid panels. 30 of these clones were mapped into the region 5q11.2-q13.3, 9 of which are flanking rate cutting BssHII-sites, known to be, often, starting points for genes. They represent excellent starting material for the development of new polymorphic markers and sequence-tagged sites, for YAC screening and building of contigs, as well as for direct isolation of genes.

Large linkage analysis in 100 families with autosomal recessive spinal muscular atrophy (SMA) and 11 CEPH families using 15 polymorphic loci in the region 5q11.2-q13.3.

The autosomal recessive proximal spinal muscular atrophy (SMA) gene was mapped to the region 5q11.2-q13.3 in 1990. Here, we present a large genetic linkage study of 100 SMA families and 11 CEPH families using 14 polymorphic simple sequence repeats (SSRs) and one RFLP in the region 5q11.2-q13.3. The genetic interval between the closest SMA flanking loci D5S435 and D5S557 comprises 1 cM at zmax = 27.94. Two recombinants were identified between the SMA gene and the closest telomeric marker D5S557 (theta = 0.02 at zmax = 8.63). The first places the SMA gene centromeric to this marker; the second suggests a double recombinant at D5S557, which is very unlikely. More likely explanations are discussed in the paper. No recombinant was found between D5S435 and the SMA gene (theta = 0.00 at zmax = 25.36). We localized a recently described polymorphic marker, D5S351 (Hudson et al., 1992), close to the SMA (theta = 0.00 at zmax = 19.01) and the 3'MAP1B gene (theta = 0.01 at zmax = 38.76). Due to its high PIC value of 0.70, it represents a very useful marker for prenatal diagnosis. In addition, we developed a new reverse primer for the nearest centromeric locus D5S435 (Soares et al., 1993), a useful marker for prenatal diagnosis, which has been very difficult to amplify in the past. Three of the markers presented here are newly developed polymorphic SSRs (one tetranucleotide repeat, D5S507/W15CATT, and two dinucleotide repeats, D5S544/C88.2GT and D5S682/C88.3GT). These markers are too far from the SMA gene to be relevant for cloning; nevertheless, as part of the human genome project, they are contributing to the fine genetic mapping of the region 5q11.2-q13.3. The most likely order of the loci based on two-point and multipoint linkage analyses as well as on specific recombination events and physical mapping studies is D5S76-D5S507- D5S6-D5S125-D5S680-D5S435-SMA-D5S557- D5S351-5'MAP1B-3'MAP1B-JK53CA1/2-(D5S127- D5S39)-(D5S544-D5S682). In general, the genetic distances obtained from the SMA and CEPH families are comparable.