AUTHOR=Wieland Ilse , Schanze Ina , Felgendreher Ina Marianti , Barthlen Winfried , Vogelgesang Silke , Mohnike Klaus , Zenker Martin 

TITLE=Integration of genomic analysis and transcript expression of ABCC8 and KCNJ11 in focal form of congenital hyperinsulinism

JOURNAL=Frontiers in Endocrinology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/endocrinology/articles/10.3389/fendo.2022.1015244

DOI=10.3389/fendo.2022.1015244

ISSN=1664-2392

ABSTRACT=<sec><title>Background</title><p>The focal form of CHI is caused by an autosomal recessive pathogenic variant affecting the paternal homologue of genes <italic>ABCC8</italic> or <italic>KCNJ11</italic> and a second somatic event specifically occurring in the affected islet of Langerhans. The approach of this study was to integrate the genetic changes occurring in pancreatic focal lesions of CHI at the genomic and transcriptional level.</p></sec><sec><title>Research Design and Methods</title><p>Patients receiving therapeutic surgery and with proven <italic>ABCC8</italic> or <italic>KCNJ11</italic> pathogenic variants were selected and analyzed for loss of heterozygosity (LOH), changes in copy number and uniparental disomy (UPD) on the short am of chromosome 11 by molecular microarray analysis and methylation-specific MLPA. Gene expression was analyzed by RT-PCR and Massive Analysis of cDNA Ends (MACE).</p></sec><sec><title>Results</title><p>Both genes, <italic>ABCC8</italic> and <italic>KCNJ11</italic>, are located in proximity to the Beckwith-Wiedemann (BWS) imprinting control region on chromosome 11p15. Somatic paternal uniparental isodisomy (UPD) at chromosome 11p was identified as second genetic event in focal lesions resulting in LOH and monoallelic expression of the mutated <italic>ABCC8/KCNJ11</italic> alleles. Of five patients with samples available for microarray analysis, the breakpoints of UPD on chromosome 11p were different. Samples of two patients were analyzed further for changes in gene expression. Profound downregulation of growth suppressing genes <italic>CDKN1</italic> and <italic>H19</italic> was detected in focal lesions whereas growth promoting gene <italic>ASCL2</italic> and pancreatic transcription factors of the endocrine cell lineage were upregulated.</p></sec><sec><title>Conclusions</title><p>Paternal UPD on the short arm of chromosome 11 appears to be the major second genetic event specifically within focal lesions of CHI but no common breakpoint for UDP can be delineated. We show for the first time upregulation of growth promoting <italic>ASCL2</italic> (achaete-scute homolog 2) suggestive of a driving factor in postnatal focal expansion in addition to downregulation of growth suppressing genes <italic>CDKN1C</italic> and <italic>H19</italic>.</p></sec>