Function of the histone demethylase PHF8 in neural progenitor cells and glial differentiation

• Autores: Simona Iacobucci
• Directores de la Tesis: María Ángeles Martínez Balbás (dir. tes.), Pedro Martínez Serra (tut. tes.)
• Lectura: En la Universitat de Barcelona ( España ) en 2021
• Idioma: español
• Tribunal Calificador de la Tesis: Guillermo Pablo Vicent Martínez (presid.), Mónica Suelves Esteban (secret.), Naiara Aquizu López (voc.)
• Programa de doctorado: Programa de Doctorado en Genética por la Universidad de Barcelona
• Materias:
  • Ciencias de la vida
    • Genética
    • Biología molecular
• Enlaces
  • Tesis en acceso abierto en: TESEO
• Resumen

  • PHF8 is a histone demethylase that has been involved in many biological processes ranging from transcription, cell cycle and DNA repair to neurodevelopment, X-linked intellectual disabilities and cancer. We studied PHF8 function in astrocytes differentiation and neural stem cells. We found that PHF8 promotes neural stem cells (NSCs) differentiation towards astrocytes facilitating the transcription of the master regulator of astrocytes differentiation Nfia and of many synaptogenic genes expressed by astrocytes (Thbs1, Sparc, Gpc4). PHF8 deficiency induces profound alterations in astrocytes differentiation and in the formation and function of excitatory synapses in vitro. We defined the astrocytes PHF8 KD defective because they don’t express GFAP properly and they misexpress some genes typical of oligodendrocyte lineage: OLIG2 and NG2. We demonstrated that genes involved in synapse formation and maturation are directly regulated by PHF8 in astrocytes. In the last years, it became clear the importance of astrocytes in promoting synapse formation, pruning aberrant synapse and regulating synaptic plasticity. We concluded that the major role of PHF8 in astrocytes is to demethylate H4K20me1, preventing subsequent ectopic heterochromatin formation, at those genes essential in the differentiation process and during synaptogenesis.

    To investigate PHF8 function in NSCs, we first analysed PHF8 KD cells phenotype. As demonstrated in other cell lines, we found that NSCs PHF8 KD suffer cell cycle delay; flow-cytometry experiment showed a delay in G1/S transition and consequently delayed cell growth. Then, we demonstrated that PHF8 depletion in NSCs affects the serine biosynthesis pathway leading to low levels of serine in PHF8 depleted cells. Indications that de novo serine metabolism could be affected in PHF8 depleted NSCs came from the RNA-seq analysis, in which we found that two key enzymes in serine biosynthesis, PHGDH and PSAT1, were both downregulated in PHF8 KD NSCs compared to CTR cells. We confirmed that PSAT1 is downregulated in PHF8 KD HeLa too, suggesting that PHF8 depletion could impair serine metabolism in different cell types or, at least, in high proliferating cells like NSCs and cancer cells. PHF8, probably cooperating with c-MYC, regulates two major enzymes involved in serine biosynthesis demethylating H4K20me1 on PHGDH and PSAT1 TSS.