Brain organoid models reveal mechanisms linked to virus-induced microcephaly Researchers at IMBA - Institute of Molecular Biotechnology of the Austrian Academy of Sciences - demonstrate that different viruses can lead to brain malformations through diverse mechanisms by using human brain organoid models. The results are published in the journal Cell Stem Cell. Microcephaly, a term referring to developmental malformations of the fetal brain, can be caused by diverse infections during pregnancy. The infectious agents in question are grouped under the general term of TORCH pathogens, in reference to Toxoplasma gondii, Other, Rubella, Human Cytomegalovirus (HCMV), Herpes Simplex Viruses 1 and 2 (HSV-1 and HSV-2), as well as the more recently emerged Zika virus (ZIKV), which was also added to the group. The question whether all TORCH pathogens lead to microcephaly through the same mechanism has remained obscured due to the absence of suitable experimental models. Now, a team of researchers around IMBA Scientific Director Jürgen Knoblich provides the first comparative analysis of mechanisms linked to virus-induced microcephaly using a human brain organoid (HBO) model derived from human pluripotent stem cells (hPSCs).