Genome sequencing and transcriptome profiling in twins discordant for Mayer-Rokitansky-Küster-Hauser syndrome

Abstract

ObjectiveMayer-Rokitansky-Küster-Hauser syndrome (MRKH) is a rare congenital disease manifesting with aplasia or severe hypoplasia of uterine structures. Even though extensive studies have been performed, for the majority of cases the etiology remains unclear. In this study, we sought to identify genetic causes in discordant monozygotic (MZ) twins using genome sequencing of blood of both twins as well as uterine tissue of the affected twin. In addition, we profiled the endometrial transcriptome of affected twins to compare perturbations with those of sporadic MRKH cases.ResultsFirst, analyzing the data under the assumption that a variant solely identified in the affected twin or affected tissue could cause the phenotype, we identified a mosaic variant in ACTR3B with a high allele frequency in affected tissue, a low allele frequency in blood of the affected twin and almost absent in the blood of the unaffected twin. Since ACTR3B has not been reported for genitourinary anomalies before, clinical relevance of the variant needs to be clarified.Second, examining the data for candidate genes previously implied in MRKH, we detected a pathogenic variant in GREB1L in one twin pair and their unaffected mother showing a reduced phenotypic penetrance. Furthermore, two variants of unknown clinical significance in PAX8 and WNT9B were identified. Analysis for copy number and structural variants revealed no discordant variants in the twins or variants in candidate genes or regions.Third, we conducted transcriptome analysis of affected tissue and observed widespread perturbations largely similar to those in sporadic MRKH cases. These shared transcriptional changes were enriched for terms associated with estrogen and its receptors pointing at a key role of estrogen in MRKH pathology.ConclusionOur study on genome sequencing of blood and uterine tissue of discordant twins is the most extensive study performed on twins discordant for MRKH so far. Nevertheless, no clear pathogenic differences in the twins or between blood and tissue samples were detected. This points towards a more complex etiology of MRKH less dependent on genetic differences and more determined by epigenetic changes or environmental factors. Our transcriptome data showed a clear overlap with gene expression data of sporadic MRKH cases, indicating that the etiology for MRKH in discordant twins and sporadic cases is largely similar.

Genetics of Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome: advancements and implications

“…Buchert et al. reported a stop-gain variant in a monozygotic twin-pair discordant for MRKH syndrome with the other twin having unilateral renal agenesis ( 98 ). Most recently, Jolly et al.…”

“…Wnt9b is expressed in the Wolffian duct epithelium providing signals guiding MD elongation ( 144 ). WNT9B has therefore been considered a candidate gene in MRKH syndrome and has been investigated in several studies identifying a total of 9 sequence variants in MRKH syndrome type I, of these 7 missense variants ( Table 2 ) ( 98 , 103 , 113 , 114 ). One patient has been reported with two variants ( 114 ).…”

“…Optical genome mapping is a newer cytogenomic method with higher resolution for the detection of both imbalanced and balanced structural variation and has recently been applied in a study by Brakta et al (73). In more recent years, whole-exome and wholegenome sequencing analyses have been applied for genome-wide detection of genetic variation at the nucleotide level (74,75,(96)(97)(98)(99)(100)(101)(102)(103)(104)(105). Investigations have included both extended familial cases and larger patient cohorts identifying variants of interesting genes, most notably GREB1L (99, 101, 102) and PAX8 (75).…”

“…The vast majority of studies to date have looked into germline genetic variation by analyzing DNA from blood samples. Due to the predominantly sporadic nature of MRKH syndrome and reports of discordant monozygotic twin pairs suggesting non-inherited genetic variation, researchers have also searched for somatic/ mosaic gene variation and tissue-specific differential gene methylation/expression patterns in uterine remnants to explain the disorder (35,98,(106)(107)(108).…”

“…Jacquinet et al ( 102) identified GREB1L variants in 5 of 63 (7.9%) sporadic MRKH syndrome patients and segregating variants in four multiplex families presenting renal and uterovaginal malformations. Buchert et al reported a stop-gain variant in a monozygotic twin-pair discordant for MRKH syndrome with the other twin having unilateral renal agenesis (98). Most recently, Jolly et al performed an unbiased rare variant enrichment analysis based on WES data from a large American-European cohort (n=148), identifying GREB1L as the only gene approaching exome-wide significance based on seven detected variants.…”