Tetsuya Hirota

Chromosome-band-specific painting : chromosome in situ suppression hybridization using PCR products from a microdissected chromosome band as a probe pool

SummaryWe describe a chromosome-band-specific painting method that involves (1) microdissection of the chromosome, chromosomal region or band, (2) amplification of a variety of chromosome/region/band-specific DNA fragments with the polymerase chain reaction (PCR), and (3) chromosome in situ suppression hybridization (CISS) with the direct use of the PCR products as a probe pool. With this method, it was possible 1) to paint an entire X or Y chromosome, a distal one-fourth of 2q, and only a band at 8q24.1, 2) to identify the origin of a minute marker chromosome in a mentally retarded patient, 3) to detect an X;Y translocation in another patient, and 4) to identify one human chromosome 2 in a human-mouse hybrid cell line. This method allows us to identify not only structural chromosome abnormalities at the band level, but also the origin of cytogenetically unidentifiable marker chromosomes. It will also be useful in studies of evolutionary cytogenetics.

Satellited chromosome 9 in a boy with multiple anomalies

SummaryA 5-year-old boy with multiple congenital anomalies showed a satellited long-arm chromosome 9, a previously undescribed abnormality. Various banding analyses of his chromosomes and those of his parents indicated that a reciprocal translocation, t(9;22)(q34.3;q11.21), occurred in the fathers gonad, and one of the translocation chromosomes was then transmitted to the patient. Thus, the patients karyotype was interpreted as 46,XY,-9,+psudic(9),t(9;22)(q34.3;q11.21). He showed several features similar to those of the Williams syndrome. The gene(s) responsible for the syndrome thus could be at either 9q34.3-qter or 22pter-q11.2. Southern blot analysis of the patients DNA indicated the presence of two copies of the argininosuccinate synthetase gene which had been assigned to 9q34.1-qter. In view of the fact that the 9q34.3-qter segment is monosomic in the patient, the gene locus was deduced to be at 9q34.1-q34.2 segment.

Isolation of 2 novel RFLP markers and their localization at 2q35 by microdissection and subsequent enzymatic amplification

SummaryWe previously constructed a chromosome 2q-specific genomic library and isolated a number of microclones. In the present study, we first analyzed with Southern hybridization whether any of the microclones represent restriction fragment length polymorphisms (RFLPs) and then tried to map RFLP markers physically, using the recently developed chromosome microdissection/enzymatic amplification method. Of 13 clones analyzed, two were RFLP markers; a clone, pM2C83, showed a fourallele MspI RFLP, and the other, pM2C8, a two-allele RsaI RFLP. In order to assign the two polymorphic markers, two chromosomal segments, 2q32-q35 and 2q35-qter, on the chromosome 2 from a karyotypically normal person were microdissected, and the DNA from each segment was amplified with the polymerase chain reaction (PCR) using marker sequence-specific primers. With this method, both of the clones were assigned to 2q35. These two RFLP markers must be useful for linkage analysis of genetic diseases whose loci are at around 2q35.

Micro extraction of DNA from whole blood and amniocytes

SummaryWe describe methods for extracting genomic DNA from a small amount of whole blood or cultured amniocytes. Nuclear DNA was extracted from whole blood spotted on blotting paper. Relatively large molecules of DNA with the average amount of 7–9 μg was extracted from 1 ml of blood spotted and stored for at most two years, being roughly 1/3 of that extracted directly from fresh whole blood. The estimated minimum amount of whole blood that gives a suitable autoradiogram of Southern hybridization was 0.3 ml. Another series of amounts of whole blood or an amniocyte suspension were molded in low-melting agarose into an 100 μl gel block. The DNA extracted from a block that was made from at least 0.25 ml of whole blood, or from 1.25×105 amniocytes (equivalent to 1/8 of the number of confluent cells in a 25 cm2 culture flask) resulted in one suitable Southern analysis. Both methods described here are applicable to the diagnosis of newborns and/or fetuses at risk of a genetic disease and to the diagnosis of a patient from whom a large amount of blood material is difficult to obtain. These methods also make a long-way transportation of the materials possible.