Cellular consequences of small supernumerary marker chromosome derived from chromosome 12: mosaicism in daughter and father.

Constitutional genomic imbalances are known to cause malformations, disabilities, neurodevelopmental delay, and dysmorphia and can lead to dysfunctions in the cell cycle. In extremely rare genetic conditions such as small supernumerary marker chromosomes (sSMC), it is important to understand the cellular consequences of this extra marker, as well the factors that contribute to their maintenance or elimination through successive cell cycles and phenotypic impact. The study of chromosomal mosaicism provides a natural model to characterize the effect of aneuploidy on genome stability and compare cells with the same genetic background and environment exposure, but differing in the presence of sSMC. Here, we report the functional characterization of different cell lines from two familial patients with mosaic sSMC derived from chromosome 12. We performed studies of proliferation dynamics, stability, and variability of these cells using fluorescent in situ hybridization (FISH), sister chromatid exchanges (SCE), and conventional staining. We also quantified the telomere-related genomic instability of sSMC cells using 3D telomeric profile analysis by quantitative-FISH. sSMC cells exhibited differences in the cell cycle dynamics compared to normal cells. First, the sSMC cells exhibited lower proliferation index and higher frequency of SCE than normal cells, associated with a higher level of chromosomal instability. Second, sSMC cells exhibited more telomeric-related genomic instability. Lastly, the differences of sSMC cells distribution among tissues could explain different phenotypic repercussions observed in patients. These results will help in our understanding of the sSMC stability, maintenance during cell cycle, and the cell cycle variables involved in the different phenotypic manifestations.

Cellular consequences of small supernumerary marker chromosome derived from chromosome 12: mosaicism in daughter and father

Constitutional genomic imbalances are known to cause malformations, disabilities, neurodevelopmental delay, and dysmorphia and can lead to dysfunctions in the cell cycle. In extremely rare genetic conditions such as small supernumerary marker chromosomes (sSMC), it is important to understand the cellular consequences of this extra marker, as well the factors that contribute to their maintenance or elimination through successive cell cycles and phenotypic impact. The study of chromosomal mosaicism provides a natural model to characterize the effect of aneuploidy on genome stability and compare cells with the same genetic background and environment exposure, but differing in the presence of sSMC. Here, we report the functional characterization of different cell lines from two familial patients with mosaic sSMC derived from chromosome 12. We performed studies of proliferation dynamics, stability, and variability of these cells using fluorescent in situ hybridization (FISH), sister chromatid exchanges (SCE), and conventional staining. We also quantified the telomere-related genomic instability of sSMC cells using 3D telomeric profile analysis by quantitative-FISH. sSMC cells exhibited differences in the cell cycle dynamics compared to normal cells. First, the sSMC cells exhibited lower proliferation index and higher frequency of SCE than normal cells, associated with a higher level of chromosomal instability. Second, sSMC cells exhibited more telomeric-related genomic instability. Lastly, the differences of sSMC cells distribution among tissues could explain different phenotypic repercussions observed in patients. These results will help in our understanding of the sSMC stability, maintenance during cell cycle, and the cell cycle variables involved in the different phenotypic manifestations.

[Recessive type of Freeman-Sheldon syndrome - report of two affected siblings] / Forma recessiva da síndrome de Freeman-Sheldon - relato de dois irmãos afetados.

OBJECTIVE: To share knowledge and information about the peculiarities of the Freeman-Sheldon syndrome, especially concerning the high risk of recurrence of its recessive type in siblings, and to stress the importance of genetic counseling for families after the birth of an affected child. DESCRIPTION: The authors describe and comment two pediatric cases of the Freeman-Sheldon syndrome in siblings born to healthy parents. These two cases present significant peculiarities that contradict the findings of the medical literature, obtained through bibliographic research about the subject. The cases described here corroborate the existence of a recessive type of the Freeman-Sheldon syndrome. In spite of the fact that some authors suggest a high frequency of severe neurological impairment in this type of syndrome, the two cases we analyzed did not show any apparent manifestation of such sequelae. COMMENTS: The Freeman-Sheldon syndrome is heterogeneous not only in its clinical presentation but also in its genetic transmission. It is very important to be informed about the existence of more than one form of hereditary transmission of this syndrome, since genetic counseling should take into consideration all possibilities. In these cases, the use of empiric risks of recurrence would be justified.