ZNF865, one of thousands of proteins in the human genome with an unknown function, acts as a switch between healthy and senescent intervertebral disc cells: silencing its gene triggered cellular senescence, pain and disc degeneration, while restoring its activity reversed senescence
ZNF865, one of thousands of proteins in the human genome with an unknown function, acts as a switch between healthy and senescent intervertebral disc cells: silencing its gene triggered cellular senescence, pain and disc degeneration, while restoring its activity reversed senescence
On October 9, Aging Cell published the first functional characterization of ZNF865 (BLST), conducted by an engineering laboratory at the University of Utah that studies intervertebral disc repair. Silencing the gene in healthy human disc cells triggers cellular senescence and DNA damage, while restoring its activity in senescent cells from patients with back pain reverses both processes. Direct injection of a gene-silencing construct into rat discs caused degeneration and increased pain sensitivity within 5–8 weeks.
Robby Bowles leads a biomedical engineering laboratory at the University of Utah. Several years ago, his team was using a CRISPR screen to identify genes for tissue-engineered discs when they came across ZNF865, a protein with no published function. Initially, they simply used it to grow disc tissue. Additional measurements of gene activity unexpectedly showed that the gene affected DNA repair and cellular senescence. “In short, it regulates cellular senescence, which is highly relevant to aging and has applications in musculoskeletal disease,” Bowles says.
The protein turned out to be a zinc finger, a structure that binds to DNA and switches nearby genes on or off. Its abundance in human and mouse disc cells declines with age and disc degeneration. Disc degeneration accounts for about 40% of back pain cases, and back pain is one of the leading causes of disability worldwide. When the authors activated ZNF865 in kidney, adipose tissue and intervertebral disc cells, it affected the same small set of pathways in all three cell types: cell division, DNA repair and cellular senescence.
When the researchers silenced ZNF865 in healthy disc cells, three markers of cellular senescence rose by a factor of 4,7–6,9, and DNA damage also increased three weeks later. Restoring the activity of the same gene in disc cells from patients with back pain had the opposite effect: cellular senescence and DNA damage decreased, levels of nine out of ten inflammatory proteins that senescent cells typically release into surrounding tissue (SASP) fell, and collagen production increased. The cells became almost indistinguishable from healthy cells in terms of DNA accessibility, with the difference narrowing by 94%.
The final step was to test the effect in a living organism. The researchers injected a construct that silences ZNF865 into a rat disc under X-ray guidance. After 5–8 weeks, the animals showed increased pain sensitivity and more signs of degeneration, and one of the two discs had lost height. Most rat models of disc degeneration produce these changes through needle puncture or enzyme treatment; here, silencing a single gene was enough to cause them.
The authors describe ZNF865 as a potential therapeutic target for cellular senescence and DNA damage across tissues: the gene is active in all human cell types, and a rare inherited mutation in it affects the joints, muscles, skin, vision and hearing.
ZNF865 is the second zinc finger protein with a previously unknown function to be identified this year as a regulator of cellular senescence. In July, the same role was reported for ZNF512B, which repairs damaged regions of DNA and suppresses the same SASP profile through chromatin repair.
Bowles is already working to develop the finding into a therapy: “Our approaches mainly involve injections, which are easier for patients and could reduce opioid use.” He says the laboratory is preparing to test the same gene in diseases such as Parkinson’s, where cellular senescence also damages neurons.