FISH

SMALL SUPERNUMERARY MARKER CHROMOSOMES

-  sSMC -

BASICS - UNIPARENTAL DISOMY

 

sSMC and uniparental disomy (UPD)

 

For more details on UPD please see here.

 

Small supernumerary maker chromosomes (sSMC) and uniparental disomy (UPD) is rare, combination of both are rarely encountered. Accordingly only 46 sSMC cases with UPD are reported. Irrespective of its rareness, UPD has to be considered especially in prenatal cases with sSMC. Here we reviewed all sSMC cases with UPD (sSMCU+) and compared them to sSMC without UPD (sSMCU-). It resulted in following correlations: i) every sSMC, irrespective of its chromosomal origin maybe principally connected with UPD, ii) mixed hetero- and iso UPD (hUPD/iUPD) can be observed most oftenly in sSMCU+ cases followed by complete iUPD, complete hUPD and segmental iUPD. iii) UPD of chromosomes #6, #7, #14, #15, #16 and #20 are most often reported in sSMCU+, iv) maternal UPD was approximately nine times more frequent than paternal, v) if mosaic with a normal cell line, acrocentric derived sSMC had three times higher chances of occurence than its corrosponding non-mosaic sSMC cases , vi) UPD in connection with a parentally inherited sSMC is, if existent at all, a rare event, vii) The gender type and shape of sSMC had no effect on UPD formation.Overall, sSMCU+ cases may have a story to tell about ‘chromosome number control mechanisms’ in early embryogenesis. {174}

 

References