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Y Kazuki

Publications and source records attributed to Y Kazuki.

6 recordsLinked to original sources
PubMed2003

A new mouse model for Down syndrome.

Trisomy 21 (Ts21) is the most common live-born human aneuploidy and results in a constellation of features known as Down syndrome (DS). Ts21 is a frequent cause of congenital heart defects and the leading genetic cause of mental retardation. Although overexpression of a gene(s) or gene cluster on human chromosome 21 (Chr 21) or the genome imbalance by Ts21 has been suggested to play a key role in bringing about the diverse DS phenotypes, little is known about the molecular mechanisms underlying the various phenotypes associated with DS. Four approaches have been used to model DS to investigate the gene dosage effects of an extra copy of Chr 21 on various phenotypes; 1) Transgenic mice overexpressing a single gene from Chr 21, 2) YAC/BAC/PAC transgenic mice containing a single gene or genes on Chr 21, 3) Mice with intact/partial trisomy 16, a region with homology to human Chr 21 and 4) Human Chr 21 transchromosomal (Tc) mice. Here we review our new model system for the study of DS using the Tc technology, including the biological effects of an additional Chr 21 in vivo and in vitro.

Animals↗
PubMed2002

The use of chromosome-based vectors for animal transgenesis.

This article summarizes our efforts to use chromosome-based vectors for animal transgenesis, which may have a benefit for overcoming the size constraints of cloned transgenes in conventional techniques. Since the initial trial for introducing naturally occurring human chromosome fragments (hCFs) with large and complex immunogulobulin (Ig) loci into mice we have obtained several lines of trans-chromosomic (Tc) mice with transmittable hCFs. As expected the normal tissue-specific expression of introduced human genes was reproduced in them by inclusion of essential remote regulatory elements. Recent development of 'chromosome cloning' technique that enable construction of human artificial chromosomes (HACs) containing a defined chromosomal region should prevent the introduction of additional genes other than genes of interest and thus enhance the utility of chromosome vector system. Using this technique a panel of HACs harboring inserts ranging in size from 1.5 to 10 Mb from three human chromosomes (hChr2, 7, 22) has been constructed. Tc animals containing the HACs may be valuable not only as a powerful tool for functional genomics but also as an in vivo model to study therapeutic gene delivery by HACs.

Animals↗
PubMed2001

Mice containing a human chromosome 21 model behavioral impairment and cardiac anomalies of Down's syndrome.

Trisomy 21 (Ts21) is the most common live-born human aneuploidy; it results in a constellation of features known as Down's syndrome (DS). Ts21 is the most frequent cause of congenital heart defects and the leading genetic cause of mental retardation. To investigate the gene dosage effects of an extra copy of human chromosome 21 (Chr 21) on various phenotypes, we used microcell-mediated chromosome transfer to create embryonic stem (ES) cells containing Chr 21. ES cell lines retaining Chr 21 as an independent chromosome were used to produce chimeric mice with a substantial contribution from Chr 21-containing cells. Fluorescence in situ hybridization and PCR-based DNA analysis revealed that Chr 21 was substationally intact but had sustained a small deletion. The freely segregating Chr 21 was lost during development in some tissues, resulting in a panel of chimeric mice with various mosaicism as regards retention of the Chr 21. These chimeric mice showed a high correlation between retention of Chr 21 in the brain and impairment in learning or emotional behavior by open-field, contextual fear conditioning and forced swim tests. Hypoplastic thymus and cardiac defects, i.e. double outlet right ventricle and riding aorta, were observed in a considerable number of chimeric mouse fetuses with a high contribution of Chr 21. These chimeric mice mimic a wide variety of phenotypic traits of DS, revealing the utility of mice containing Chr 21 as unique models for DS and for the identification of genes responsible for DS.

Animals↗
PubMed2001

Germline transmission of a transferred human chromosome 21 fragment in transchromosomal mice.

We generated transchromosomal (Tc) mice containing a human chromosome 21 fragment (hCF21) using mouse embryonic stem (ES) cells with the transferred hCF21. Here we report breeding analyses that test the maintenance rate of the hCF21 in Tc mice of two different genetic backgrounds, MCH (ICR) and C57BL/6. Fluorescence in situ hybridization and polymerase chain reaction-based DNA analyses revealed that the structure of the hCF21 fragment including the CBR1, SIM2, HLCS, and D21S268 markers, was approximately 5 Mb in size, and was transmitted at least to the F3 generation. Though the retention rate of the hCF21 was variable among individual mice, for example, 21%-92% in brain and 10%-92% in tail fibroblasts, the C57BL/6 background yielded a higher retention rate than did the MCH (ICR). These results suggest that the hCF21 could be maintained stably in Tc mice, depending on the genetic background. The panel of Tc mice will be a useful model to investigate the function of genes on the hCF21 fragment in various tissues through germinal transmission.

Animals↗
PubMed2000

Manipulation of human minichromosomes to carry greater than megabase-sized chromosome inserts.

For introducing regions of human chromosomes greater than a megabase into cells or animals, we have developed a chromosome-cloning system in which defined regions of human chromosomes can be cloned into a stable human minichromosome vector in homologous recombination-proficient chicken DT40 cells. The stable minichromosome vector allowed a 10 Mb-sized region of the mitotically unstable human chromosome 22 to be stably maintained in mouse embryonic stem (ES) cells, and in mice. Furthermore, we demonstrated functional expression of human genes from the HAC in mice. This study describes a stable cloning and expression system for greater than megabase-sized regions of human chromosomes.

Animals↗