title: Demonstration of Autosomal Monoallelic Expression in Thyroid Tissue Assessed by Whole-Exome and Bulk RNA Sequencing.
abstract: Congenital hypothyroidism due to thyroid dysgenesis (CHTD) is a disorder with a prevalence of 1/4000 live births, the cause of which remains unknown. The most common diagnostic category is thyroid ectopy, which occurs in up to 80% of CHTD cases. CHTD is predominantly not inherited and has a high discordance rate (>92%) between monozygotic (MZ) twins. The sporadic nature of CHTD might be explained by somatic events such as autosomal monoallelic expression (AME), given that genes expressed in a monoallelic way are more vulnerable to otherwise benign monoallelict genetic or epigenetic mutations.
  
  
  
  The aim of this study was to search for complete (90%) AME in normal and dysgenetic thyroid tissues.
  
  
  
  Aggregated analysis of whole-exome and bulk RNA sequencing was performed on two ectopic thyroids, four normal thyroids, and the human thyroid cell line Nthy-ori.
  
  
  
  A median of 5062 (range 2081-5270) genes per sample showed sufficient numbers of heterozygous single nucleotide polymorphisms to be informative. The median monoallelic expression represented 22 (range 16-32) of the informative genes for each thyroid sample. Examples of genes displaying AME are FCGBP, ZNF331, USP10, BCLAF1, and some HLA genes; these genes are involved in epithelial-mesenchymal transition, cell migration, cancer, and immunity.
  
  
  
  AME may account for the high discordance rate observed between MZ twins and for the sporadic nature of CHTD. These findings also have implications for other pathologies, including cancers and autoimmune disorders of the thyroid.
authors.affiliation: 1 Endocrinology Service and Research Center, Sainte-Justine University Hospital Center, Department of Pediatrics, Université de Montréal , Montreal, Canada .|2 Department of Biomedical Sciences, Université de Montréal , Montreal, Canada .
authors.forename: Fabien
authors.initials: F
authors.lastname: Magne
authors.affiliation: 3 Department of Human Genetics, McGill University , Montreal, Canada .
authors.forename: Bing
authors.initials: B
authors.lastname: Ge
authors.affiliation: 1 Endocrinology Service and Research Center, Sainte-Justine University Hospital Center, Department of Pediatrics, Université de Montréal , Montreal, Canada .
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Larrivée-Vanier
authors.affiliation: 1 Endocrinology Service and Research Center, Sainte-Justine University Hospital Center, Department of Pediatrics, Université de Montréal , Montreal, Canada .
authors.forename: Guy
authors.initials: G
authors.lastname: Van Vliet
authors.affiliation: 1 Endocrinology Service and Research Center, Sainte-Justine University Hospital Center, Department of Pediatrics, Université de Montréal , Montreal, Canada .|4 Department of Medicine, Université de Montréal , Montreal, Canada .
authors.forename: Mark E
authors.initials: ME
authors.lastname: Samuels
authors.affiliation: 3 Department of Human Genetics, McGill University , Montreal, Canada .
authors.forename: Tomi
authors.initials: T
authors.lastname: Pastinen
authors.affiliation: 1 Endocrinology Service and Research Center, Sainte-Justine University Hospital Center, Department of Pediatrics, Université de Montréal , Montreal, Canada .|2 Department of Biomedical Sciences, Université de Montréal , Montreal, Canada .|5 Department of Biochemistry, Université de Montréal , Montreal, Canada .
authors.forename: Johnny
authors.initials: J
authors.lastname: Deladoëy
mesh_terms: D000293:Adolescent; D000483:Alleles; D002648:Child; D002675:Child, Preschool; D003409:Congenital Hypothyroidism / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D059472:Exome; D005260:Female; D006801:Humans; D008297:Male; D020641:Polymorphism, Single Nucleotide; D013961:Thyroid Gland / Q000378:metabolism*; D000073359:Exome Sequencing