Browsing by Author "Trindade, Marlene Pacheco"
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- Maternal thyroid hormones role in zebra fish blood-hindbrain barrier developmentPublication . Trindade, Marlene Pacheco; Campinho, António do Nascimento Sequeira de JesusThyroid hormones (THs), thyroxine (T4) and 3,5,3’–triiodothyronine (T3), are key signalling molecules that regulate vertebrate development and physiology. In humans, an inadequate supply of THs during prenatal stages causes several neurological impairments, affecting a newborn’ psychomotor and cognitive development. The most severe condition results from mutations of the monocarboxylate transporter 8 (MCT8), leading to a rare X-linked neurodevelopmental disorder, the Allan-Herndon-Dudley syndrome (AHDS). In zebrafish, knockdown of the T3 exclusive membrane transporter Mct8 phenocopies the symptoms observed in AHDS patients. An impaired blood-hindbrain barrier (BHB) was observed in zebrafish but has not yet been confirmed in humans. This thesis aimed to understand how maternal T3 (MT3) through Mct8 coordinates the development of the vascular system of the zebrafish hindbrain. Transcriptome analysis of 25 hours post fertilisation (hpf) CTRMO vs MCT8MO zebrafish embryos revealed that expression of several genes of the important angiogenic Vegf pathway was significantly regulated by MT3. At the cellular level, specific vegfaa signalling juxtaposed to the developing central arteries (CtAs) was identified and vegfaa-165 mRNA rescues the majority of CtAs in MCT8MO zebrafish embryos. To identify the source of hindbrain vegfaa and, consequently, the cell identity dependent on MT3 signalling, neural cell markers were analysed. This revealed that pax8 inhibitory interneurons and cpne4 intrinsic digit-innervating motor neurons were under MT3 regulation but were not responsible for CtA development. pax6a neural progenitor cells (NPCs) were the source of hindbrain vegfaa, and a correlation between these cells and the migratory behaviour of the CtAs was found. Colocalisation analysis of pax6a NPCs with thraa, thrab and mct8 demonstrated that these cells were regulated in a cell-autonomous way and showed that the spatiotemporal expression could be an indicator of the timely sprouting of each CtA during BHB development. Finally, pax6a loss-of-function CRISPR/Cas9 zebrafish embryos had a similar hindbrain vascular impairment as the MCT8MO zebrafish embryos, confirming that pax6a NPCs were the cells responsible for CtA ingression into the hindbrain. In conclusion, MT3 via Mct8 is important for the survival and proliferation of pax6a NPCs, which are the instructing source of vegfaa necessary for the timely development of the BHB CtAs.