CDKN1C hyperexpression in two patients with severe growth failure and microdeletions affecting the paternally inherited KCNQ1OT1:TSS-DMR
Kaori Hara-Isono1,2, Kazuki Yamazawa3, Satsuki Tanaka4
1Department of Molecular Endocrinology, National Research Institute for Child Health and Development, Tokyo, Japan.
Background:
Two imprinting control centres, H19/IGF2:IG-differentialy methylated region (DMR) and KCNQ1OT1:TSS-DMR, reside on chromosome 11p15.5. Paternal deletions involving the KCNQ1OT1:TSS-DMR result in variable phenotypes, namely, normal phenotype, Silver-Russel syndrome (SRS) and fetal demise. However, expression analyses for CDKN1C in these patients are very limited.
Cases:
Patient 1 (adult woman) and patient 2 (boy in early childhood) showed prenatal and postnatal growth failure and clinical suspicion of SRS.
Molecular Analyses:
Both patients showed hypermethylation of the KCNQ1OT1:TSS-DMR caused by the paternal heterozygous de novo deletions involving the KCNQ1OT1:TSS-DMR, but not including CDKN1C enhancers. The deletion sizes were 5 kb and 12 kb for patients 1 and 2, respectively. CDKN1C gene expressions in immortalised leucocytes of both patients were increased compared with those of controls.
Conclusion:
Paternal deletions involving the KCNQ1OT1:TSS-DMR, but not including CDKN1C enhancers, disrupt KCNQ1OT1 expression, strongly activate CDKN1C expression and consequently cause severe growth failure.
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