ZNF644

ZNF644 is a core subunit of the G9a/GLP histone H3K9 methyltransferase complex, where it uses its zinc finger motifs to recognize specific DNA sequences and recruit G9a/GLP to chromatin, thereby mediating H3K9 mono- and dimethylation and transcriptional repression (PMID:25789554). Missense mutations in ZNF644 co-segregate with autosomal dominant high myopia in affected families, consistent with its expression in retinal and retinal pigment epithelium cells (PMID:21695231). ZNF644 also promotes cell cycle progression and survival, as its knockdown arrests cells in G1/G2 phases and induces apoptosis (PMID:30021720).

1. 2011 Medium

   Exome sequencing in myopia families revealed that ZNF644 harbors missense mutations co-segregating with autosomal dominant high myopia, establishing it as a candidate disease gene expressed in retinal tissue but leaving its molecular function undefined.

   Evidence Exome sequencing with Sanger validation and expression analysis in human retinal/RPE cells

   PMID:21695231

   Open questions at the time

   • No functional reconstitution showing how specific mutations alter ZNF644 activity
   • Molecular targets and binding partners of ZNF644 in the retina remain unknown
   • Co-segregation data without independent replication in additional cohorts
2. 2015 High

   Biochemical characterization resolved ZNF644's molecular function: it is a DNA-binding subunit of the G9a/GLP complex that targets this histone methyltransferase to specific genomic loci for H3K9 methylation and gene repression, answering how G9a/GLP achieves locus-specific chromatin modification.

   Evidence Unbiased protein affinity purification, reciprocal Co-IP, zinc finger DNA-binding assays, chromatin recruitment assays, and H3K9 methylation readouts

   PMID:25789554

   Open questions at the time

   • Structural basis of ZNF644–G9a interaction not determined
   • Whether myopia-associated mutations disrupt G9a recruitment or DNA binding is untested
   • Genome-wide map of ZNF644-directed G9a/GLP target loci not established
3. 2018 Medium

   Functional studies showed that ZNF644 is required for cell cycle progression and survival in Sertoli cells and is post-transcriptionally regulated by miR-362, extending its role beyond chromatin regulation to proliferation control.

   Evidence Dual luciferase reporter assay confirming miR-362 targeting of ZNF644 3′UTR; siRNA knockdown with flow cytometry, proliferation, and apoptosis assays in porcine immature Sertoli cells

   PMID:30021720

   Open questions at the time

   • Single-lab study in a porcine model; not independently confirmed in other species
   • Whether ZNF644's pro-proliferative role depends on its G9a/GLP-targeting function is unknown
   • Downstream transcriptional targets mediating cell cycle effects not identified

• It remains unknown how myopia-associated ZNF644 mutations alter G9a/GLP chromatin targeting, what the full set of ZNF644-directed target genes is in retinal tissue, and whether ZNF644's role in cell cycle control operates through H3K9 methylation.
• No structure of ZNF644 or ZNF644–G9a complex available
• ChIP-seq for ZNF644 in retinal cells not performed
• Mechanistic link between ZNF644 mutations and myopia pathogenesis not established