Recurrent chromosomal alterations are found in roughly 20% of all uterine fibroids but in the majority cytogenetic changes are lacking. Recently, mutations of the gene mediator subcomplex 12 (MED12) have been detected in a majority of fibroids but no information is available whether or not they co-occur with cytogenetic subtypes as, e.g., rearrangements of the genes encoding high mobility group AT-hook (HMGA) proteins. In a total of 80 cytogenetically characterized fibroids from 50 patients, we were not only able to confirm the frequent occurrence of MED12 mutations but also to stratify two mutually exclusive pathways of leiomyomagenesis with either rearrangements of HMGA2 reflected by clonal chromosome abnormalities affecting 12q14~15 or by mutations affecting exon 2 of MED12. On average the latter mutations were associated with a significantly smaller tumor size. However, G>A transitions of nucleotides c.130 or c.131 correlate with a significantly larger size of the fibroids compared to other MED12 mutations thus explaining the high prevalence of the former mutations among clinically detectable fibroids. Interestingly, fibroids with MED12 mutations expressed significantly higher levels of the gene encoding wingless-type MMTV integration site family, member 4 (WNT4). Based on these findings and data from the literature, we hypothesize that estrogen and the mutated MED12 cooperate in activating the Wnt pathway which in turn activates b-catenin known to cause leiomyoma-like lesions in a mouse model. The occurrence of a ''fibroid-type mutation'' in a rare histologic subtype of endometrial polyps suggests that this mechanism is not confined to uterine leiomyomas.Uterine leiomyomas (syn.: fibroids) are among the most frequent clinically relevant human tumors leading, e.g., to abdominal pain, bleeding and infertility. Their prevalence clearly differs depending on ethnicity but in most countries exceeds 50% of all women in their reproductive ages.
Karyotyping of dog chromosomes is a difficult task owing to the high diploid number of chromosomes (2n = 78) and the similar morphology of autosomes, all of which are acrocentrics. In this report 22 of the 39 G-banded chromosome pairs and their corresponding ideograms have been standardized. The ideogram comprises altogether 235 bands. The need for the introduction of molecular techniques such as chromosome painting and physical mapping of genetic markers for the identification of small acrocentrics is discussed.
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