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YAC and cosmid contigs spanning the Batten disease (CLN3) region at 16p12.1-p11.2.

A yeast artificial chromosome (YAC) contig has been constructed in 16p12.1-p11.2 that encompasses three loci (D16S288, D16S299, and D16S298) closely linked to the gene causing Batten disease or juvenile-onset neuronal ceroid lipofuscinosis (CLN3). The physical map has been ordered using 42 sequence tagged sites. Four genes, interleukin-4 receptor (IL4R), phenol-preferring phenol sulfotransferase (STP), monoamine-preferring phenol sulfotransferase (STM), and sialophorin (SPN), have been mapped to the YAC contig. A partial genomic restriction map has been constructed to confirm the order and distances between D16S298, predicted to be the locus closest to CLN3. The overlapping genomic clones are a valuable resource for cloning the Batten gene (CLN3) and other genes in the region.

Antigens, CD↗

A 1.7-megabase sequence-ready cosmid contig covering the TSC1 candidate region in 9q34.

The disease gene TSC1 has been genetically mapped to human chromosome region 9q34, in a 4-cM interval between the markers D9S149 and D9S114. Within this interval there is conflicting genetic evidence as to the finer localization of the gene. We have used finger-printing methods and hybridization to produce a 1.7-Mb overlapping clone map covering the TSC1 candidate region, with a single gap of 20 kb. We have localized 12 previously cloned genes and 17 genetic markers on this map and have confirmed the order of the genetic map. This deep set of overlapping clones is now ready to be used for candidate gene isolation, for transcription studies, or for sequencing.

Chromosome Mapping↗

Development of additional RFLP probes near the locus for Duchenne muscular dystrophy by cosmid cloning of the DXS84 (754) locus.

We have isolated 70kb of sequences surrounding probe 754 (DXS84), linked with Duchenne muscular dystrophy. In addition to the original PstI RFLP detected by 754, BglII and EcoRI RFLPs were detected with the single copy subclone 754.11 and a HindIII RFLP with the subclone 754.6. The BglII and HindIII and HindIII RFLPs both have minor allele frequencies of 40%, as in PstI polymorphism. The EcoRI polymorphism has a minor allele frequency of 23%. Since a linkage disequilbrium is observed between these RFLPs (P less than 0.001), the BglII and the HindIII RFLPs do not contribute to the heterozygosity. However, the minor allele of the EcoRI RFLP segregates exclusively with the major haplotype of the PstI-BglII-HindIII complex, and consequently 47% of the homozygotes for the haplotype become heterozygous. As a result, the overall heterozygote frequency of the DXS84 locus increases from 50% to 65%.

Chromosome Mapping↗

Some mathematical aspects of mapping DNA cosmids.

A number of experimental and mathematical problems must be solved before high resolution physical maps of mammalian chromosomes can be reliably determined. Such a map might consist of an ordered set of nonsequenced, overlapping DNA fragments 20,000-40,000 bases long, produced by digestion of a chromosome, using two restriction enzymes. Map construction requires assigning a signature to each fragment that differentiates it unambiguously from every other fragment, and then devising a computationally efficient algorithm that will provide a unique ordering of the fragments. In the first part of this paper we present a polynomial time algorithm that yields a unique map, and is largely independent of the method for assigning signatures. In the next section we analyze the distribution of lengths of restriction digest fragments and discuss the implications for the algorithm, including the expected number of map gaps. Finally, we discuss a specific method for assigning signatures proposed by Hans Lehrach, based on which of a panel of probes binds to a given fragment. In particular we examine the effects of fragment length heterogeneity on the theoretical optimum length and number of probes, and the extent to which false signatures might be obtained by nonspecific binding. We conclude that the Lehrach strategy is effective provided the number of probes is greater than or equal to 150, but that each fragment will need testing with at most 25 probes.

Algorithms↗

Identification of masked and variant Ph (complex type) translocations in CML and classic Ph in AML and ALL by fluorescence in situ hybridization with the use of bcr/abl cosmid probes.

In the present study, three chronic myelogenous leukemia (CML) patients with variant Philadelphia (Ph) chromosomes (complex types), two CML patients with a masked Ph, one case with Ph positive acute lymphocytic leukemia (ALL), and one with Ph positive acute myelocytic leukemia (AML) were analyzed by standard cytogenetic techniques (G-banding), Southern blot studies, and fluorescence in situ hybridization (FISH) procedures using probes from portions of the bcr and abl genes. It has been previously shown that this FISH approach could detect the bcr/abl fusion event in CML patients with classic or variant (simple type) Ph. Our results demonstrate that this FISH assay can also detect the bcr/abl fusion status in CML patients with masked or variant (complex type) Ph chromosomes and in some patients with Ph positive ALL or AML.

Adult↗