title: Deletion of the RNaseIII enzyme dicer in thyroid follicular cells causes hypothyroidism with signs of neoplastic alterations.
abstract: Micro-RNAs (miRNAs) are small non-coding RNAs that regulate gene expression, mainly at mRNA post-transcriptional level. Functional maturation of most miRNAs requires processing of the primary transcript by Dicer, an RNaseIII-type enzyme. To date, the importance of miRNA function for normal organogenesis has been demonstrated in several mouse models of tissue-specific Dicer inactivation. However, the role of miRNAs in thyroid development has not yet been addressed. For the present study, we generated mouse models in which Dicer expression has been inactivated at two different stages of thyroid development in thyroid follicular cells. Regardless of the time of Dicer invalidation, the early stages of thyroid organogenesis, preceding folliculogenesis, were unaffected by the loss of small RNAs, with a bilobate gland in place. Nevertheless, Dicer mutant mice were severely hypothyroid and died soon after weaning unless they were substituted with T4. A conspicuous follicular disorganization was observed in Dicer mutant thyroids together with a strong down regulation of Nis expression. With increasing age, the thyroid tissue showed characteristics of neoplastic alterations as suggested by a marked proliferation of follicular cells and an ongoing de-differentiation in the center of the thyroid gland, with a loss of Pax8, FoxE1, Nis and Tpo expression. Together, our data show that loss of miRNA maturation due to Dicer inactivation severely disturbs functional thyroid differentiation. This suggests that miRNAs are mandatory to fine-tune the expression of thyroid specific genes and to maintain thyroid tissue homeostasis.
authors.affiliation: Institut de Recherche Interdisciplinaire en Biologie Humaine et Moléculaire (I.R.I.B.H.M.), Faculté de Médecine, Université Libre de Bruxelles (ULB), Brussels, Belgium.
authors.forename: Wendy
authors.initials: W
authors.lastname: Rodriguez
authors.forename: Ling
authors.initials: L
authors.lastname: Jin
authors.forename: Véronique
authors.initials: V
authors.lastname: Janssens
authors.forename: Christophe
authors.initials: C
authors.lastname: Pierreux
authors.forename: Anne-Christine
authors.initials: AC
authors.lastname: Hick
authors.forename: Eneko
authors.initials: E
authors.lastname: Urizar
authors.forename: Sabine
authors.initials: S
authors.lastname: Costagliola
mesh_terms: D000818:Animals; D054337:Cell Dedifferentiation / Q000235:genetics; D049109:Cell Proliferation; D015536:Down-Regulation / Q000235:genetics; D004789:Enzyme Activation; D017353:Gene Deletion; D018507:Gene Expression Regulation, Developmental; D007037:Hypothyroidism / Q000201:enzymology* / Q000235:genetics; D019426:Integrases / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D009928:Organ Specificity / Q000235:genetics; D000072636:PAX8 Transcription Factor; D051761:Paired Box Transcription Factors / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D043244:Ribonuclease III / Q000235:genetics / Q000378:metabolism*; D013961:Thyroid Gland / Q000201:enzymology* / Q000254:growth & development / Q000473:pathology*; D013964:Thyroid Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000473:pathology*
chemical_list: D000072636:PAX8 Transcription Factor; D051761:Paired Box Transcription Factors; C499496:Pax8 protein, mouse; D012333:RNA, Messenger; C045073:Cre recombinase; D019426:Integrases; D043244:Ribonuclease III