The expression pattern of the Hmgic gene during development.

The technique of RNA in situ hybridization to mouse embryo sections from different developmental stages was used to perform a detailed analysis of the expression pattern of the gene for the architectural chromatin factor Hmgic. At early stages of fetal development (day 9.5 post conceptionem), Hmgic is expressed at a high rate throughout the whole embryo. In the second half of development, the pattern of expression becomes more restricted. Expression is found in mesenchymal derivatives, which differentiate into cartilage or muscle, in epithelial cell layers of the lung, pancreas, submandibular gland, and vibrissae, and in some special parts of the central nervous system. The expression pattern of Hmgic was compared with the previously reported studies of Hmgiy gene expression, another member of the Hmgic protein family, and with the expression of histone H4, Hist4, which is representative of cellular proliferation stages. In some tissues the pattern of expression for both factors coincides, but in others the expression is different. Hmgic expression correlates throughout fetal development with high proliferative activity. In contrast, Hmgiy is expressed also in tissues with no proliferative activity, such as the cortical plate of the telencephalon and the spinal cord at late gestational stages.

Isolation and characterization of the mouse homolog of SYT, a gene implicated in the development of human synovial sarcomas.

In a previous study we reported the isolation of the human synovial sarcoma-associated t(X;18) breakpoint. As a result of this translocation, the SYT gene on chromosome 18 fuses to either the SSX1 or the SSX2 gene on the X chromosome, depending on the exact location of the breakpoint within band Xp11.2. As yet, little is known about the modes of action of the SYT and SSX genes and their respective (fusion) products. Here we report the isolation of the mouse homolog of SYT, its full length cDNA sequence, its chromosomal localization, and its spatio-temporal expression patterns in adult and embryonic tissues. The SYT gene was found to be well conserved during evolution and is part of a region of synteny between the human and mouse chromosomes 18. In early embryogenesis, Syt is ubiquitously expressed. In later stages, the expression becomes confined to cartilage tissues, specific neuronal cells and some epithelial derived tissues. In mature testis, expression was specifically observed in primary spermatocytes.

N-myc expression in the embryonic cochlea of the mouse.

N-myc expression in the mouse embryo was examined during the late cochlear organogenesis. Tissue distribution of N-myc expression was histologically analyzed by in situ hybridization of the transcript in the cochlea between 15 and 18 days of gestation. At 15 days of gestation, N-myc expression was found very conspicuous in nervous structure of the cochlea such as the auditory nerve and the spiral ganglion. Moreover, N-myc was also present in the Köllikers organ and in the epithelium surrounding the cochlear canal. A few days later, N-myc expression was still clearly present in the Köllikers organ but less so in nervous structures. This study shows that cochlear tissues derived from the otic placode present a significant level of N-myc transcript during late embryogenesis. N-myc expression seems to be related to cell differentiation in the inner ear.

Aberrant Myc expression in the murine trisomy 15 syndrome is correlated with prolonged proliferation in spongiotrophoblast cells of the placenta.

In the mouse the protooncogene Myc is localized to Chromosome 15. Embryos with trisomy 15 (Ts15) are severely retarded and die in utero at an early stage. The placenta of these embryos shows enlargement of the fetal spongiotrophoblast. In the spongiotrophoblast and giant cells of the normal euploid placenta, Myc expression declines from day 10.5 of gestation onward whereas Myc expression persists at a high level in Ts15 cells. At the same time these Ts15 cells show prolonged proliferation which consequently leads to the observed enlargement of that tissue layer in Ts15 placentas.