ESPE Abstracts

Context: X chromosome inactivation (XCI) is a process in which one of the two X chromosomes in a female is randomly inactivated in order to correct gene dosage between males and females. However, about 15% of genes escape from XCI (termed escapees), and 10% of genes are variably inactivated (variable genes). The mechanism of inactivation and escape remains to be revealed. The promoter regions of escapees are hypomethylated compared to those of the inac...

Abnormal expression of imprinted genes leads to imprinting disorders (IDs). Silver-Russell syndrome (SRS) and Prader-Willi syndrome (PWS) are representative IDs showing small for gestational age and short stature (SGA-SS).Temple syndrome (TS14) caused by abnormal gene expression at the 14q32.2 imprinted region, maternal uniparental disomy of chromosome 6 (UPD(6)mat), 16 (UPD(16)mat), and 20 (UPD(20)mat) are also associated with SGA-SS. Fuethermore, some copy number variations ...

Context: Pseudohypoparathyroidism type 1B (PHP1B) caused by methylation defects of differentially methylated regions (DMRs) on the GNAS locus can be categorized into groups according to etiologies and methylation defect patterns of the DMRs. However, there are no reports evaluating the clinical differences in detail, such as diagnostic features at onset and Albright’s hereditary osteodystrophy (AHO) features, among the groups.<stro...

Loss of methylation (LOM) at GNAS-A/B:TSS-differentially methylated regions (DMRs) in the GNAS locus is observed in pseudohypoparathyroidism type 1B (PHP1B). Many PHP1B cases are sporadic, but autosomal dominant-PHP1B has a deletion involving NESP55 expressed from the maternal allele or STX16 located upstream of the GNAS locus on the maternal allele. We report the possible first familial PHP1B cases with retrotransposon insertion in the GNAS locus on the maternal allele. To ou...

Context: Maternal uniparental disomy for chromosome 20 (UPD(20)mat) resulting in aberrant expression of imprinted transcripts at the GNAS locus is a poorly characterized condition. Only 10 non-mosaic cases have been studied clinically. These patients presented with pre- and post-natal growth failure and feeding difficulties. The phenotype of these cases overlapped with that of Silver-Russell syndrome (SRS) and small for gestational age-short stature (SGA-SS); however, the etio...