Andreas Weith

Identification and mapping of six microdissected genomic DNA probes to the proximal region of mouse chromosome 1.

Six independent DNA probes, lambda Mm1C-150, lambda Mm1C-153, lambda Mm1C-156, lambda Mm1C-162, lambda Mm1C-163, and lambda Mm1C-165, have been isolated from a library of microdissected fragments from mouse chromosome 1, spanning cytogenetic bands C2 to C5. These DNA probes have been mapped by restriction fragment length polymorphism analysis with respect to 12 marker loci previously assigned to this portion of mouse chromosome 1, in a panel of 251 segregating Mus spretus x C57BL/6J interspecific backcross mice. The gene order and intergene distances were determined by segregation analysis to be centromere- lambda Mm1C-162-11.1 cM-Col3a1-8.8 cM-Len-2-2.6 cM-lambda Mm1C-163-1.6 cM-Fn-1-1.6 cM-Tp-1-0.8 cM-lambda Mm1C-165/Vil-0.4 cM-Inha-2.8 cM-lambda Mm1C-153-2.4 cM-lambda Mm1C-156-1.2 cM-Pax-3-5.6 cM-Akp-3-0.8 cM-Acrg-2.0 cM-Sag-0.5 cM-Col6a3-1.8 cM-lambda Mm1C-150-15.4 cM-Ren1,2. Four of these probes map within a chromosome 1 segment that is homologous to human chromosome 2q. Southern blotting analyses indicate that one of these anonymous probes, lambda Mm1C-165, detects DNA fragments highly conserved across species. These novel polymorphic probes should prove useful for linkage and physical mapping of this chromosomal region.

Microclones derived from the mouse chromosome 7 D−E bands map within the proximal region of the c14CoS deletion in albino mutant mice

A group of radiation-induced perinatal-lethal deletions that include the albino (c) locus on mouse chromosome 7 causes failure of expression of various hepatocyte-specific genes when homozygous (S. Gluecksohn-Waelsch, 1979, Cell 16:225-237). The transcription of such genes could be controlled in trans by a regulatory gene(s) located within the proximal region of the C14CoS deletion. To identify this potential regulatory gene, a microclone library was established from microdissected D and E bands of chromosome 7. Three nonoverlapping microclones (E305, E336B, and E453B) hybridizing with wildtype but not with C14CoS/C14CoS DNA were isolated. E336B represents a single-copy DNA fragment, whereas E305 and E453B hybridized with 3 and 10 EcoRI DNA restriction fragments, respectively. All fragments map exclusively within the deletion. The microclones hybridized to DNA of viable C6H/C14CoS deletion heterozygotes but not to DNA of homozygotes for the lethal mutation c10R75M, which belongs to the same complementation group as c14CoS. DNA of viable homozygous mutant C62DSD, which carries a deletion breakpoint proximal to that of c6H, hybridized only with E453B. This microclone identified 6 EcoRI restriction fragments in C62DSD/C62DSD DNA. The results demonstrate that of the isolated microclones, E453B identifies a locus (D7RT453B) that maps closest to the hsdr-1 (hepatocyte-specific developmental regulation) locus (S. Gluecksohn-Waelsch, 1989, Mouse Newslett. 83: 149), which maps between the proximal breakpoints of deletions c10R75M and c62DSD.

Genetic Alterations in Colorectal Cancers in Correlation to Clinical Parameters

Genetic alterations resulting in oncogenic activation of certain cellular genes or in deletion of tumor suppressor genes may play an important role in colorectal cancers. Cytogenetic and molecular genetic approaches led to the identification of non-random genetic alterations including mutational activation of RAS genes, and deletion of genetic material from various chromosomal loci. Our own systematic study of the chromosomal status of colorectal cancer cells has more recently uncovered cytogenetic evidence for DNA amplification. Our data raise the suspicion that amplification is mainly associated with an advanced or metastatic tumor stage (Dukes C or D). The study of other cancers had made evident that DNA amplification is a useful predictor for clinical outcome. Once the molecular identity of the amplified DNA in colorectal cancer is defined it should be possible to find out if amplified molecular probes may be useful for predicting the clinical behaviour of colorectal cancers.