SUMMARY Microcephaly is a neurodevelopmental disorder causing significantly reduced cerebral cortex size. Many known microcephaly gene products localize to centrosomes, regulating cell fate and proliferation. Here, we identify and characterize a nuclear zinc finger protein, ZNF335/NIF-1, as a causative gene for severe microcephaly, small somatic size, and neonatal death. Znf335-null mice are embryonically lethal and conditional knockout leads to severely reduced cortical size. RNA-interference and postmortem human studies show that Znf335 is essential for neural progenitor self-renewal, neurogenesis, and neuronal differentiation. ZNF335 is a component of a vertebrate-specific, trithorax H3K4-methylation complex, directly regulating REST/NRSF, a master regulator of neural gene expression and cell fate, as well as other essential neural-specific genes. Our results reveal ZNF335 as an essential link between H3K4 complexes and REST/NRSF, and provide the first direct genetic evidence that this pathway regulates human neurogenesis and neuronal differentiation.

Highlights d Strategy for affinity purification of native chromatin fragments d Heterochromatin and euchromatin have overlapping and non-overlapping proteomes d The heterochromatin proteome includes inner nuclear membrane proteins and nucleoporins d Inner-ring nucleoporins are required for clustering and maintenance of heterochromatin

To study the in vivo role of TFIID in the transcriptional regulation of hepatic genes, we generated mice with liver-specific disruption of the TAF10 gene. Inactivation of TAF10 in hepatocytes resulted in the dissociation of TFIID into individual components. This correlated with the downregulation of most hepatocyte-specific genes during embryonic life and a defect in liver organogenesis. Unexpectedly, however, the transcription of less than 5% of active genes was affected by TAF10 inactivation and TFIID disassembly in adult liver. The extent of changes in transcription of the affected genes was dependent on the timing of their activation during liver development, relative to that of TAF10 inactivation. Furthermore, TFIID dissociation from promoters leads to the re-expression of several postnatally silenced hepatic genes. Promoter occupancy analyses, combined with expression profiling, demonstrate that TFIID is required for the initial activation or postnatal repression of genes, while it is dispensable for maintaining ongoing transcription.