The results of DNA analysis of deletion in exons 7 and 8 of SMN gene, and exon 5 of NAIP gene in 24 SMA-families from Ukraine are presented. Deletions of SMN exons 7 and 8, or 7 were found in 46 (97.9%) of 47 SMA-chromosomes. A homozygous deletion of NAIP exon 5 was demonstrated in 4 (19%) of 21 SMA-families. The authors have demonstrated that in 2 SMA patients with homozygous deletion SMN exon 7 only, the remaining SMN exon 8 was a part of a chimeric CBCD41/SMN gene.
Pluripotent mouse P19 embryonic carcinoma cells represent a convenient in vitro model for studying various aspects of cardiac differentiation. Here by using whole-cell patch-clamp recording we have identified the rapid delayed rectifier K+ current, I(Kr) in P19 cell induced to differentiate into cardiac phenotype by DMSO (1%). Cardiac differentiation was confirmed by the appearance of spontaneously beating cells, their morphological features, ultrastructural clusterization of mitochondria around contraction elements, expression of cardiac actin mRNAs and MLC2v, and by the presence of inward sodium and calcium currents. I(Kr) was isolated based on the sensitivity to the specific blocker, E-4031, which at concentration of 1 MM blocked more than 50% of the total outward K+ current. However, in contrast to I(Kr) in native cardiac myocytes and in heterologous systems expressing I(Kr)-carrying ERG1 potassium channel, E-4031-sensitive K+ current in cardiac-like P19 cells lacked characteristic inward rectification, suggesting specific regulation and/or subunit composition of endogenous ERG -based channel in these cells. Establishing the reason(s) for this phenomenon will advance the understanding of the mechanisms of I(Kr)-channel rectification. Cardiac-differentiated P19 cells might also be useful for studying pharmacological modulation of I(Kr), which is recognized target for cardiotoxic side effects of numerous drugs.