Ubiquitin associated protein 1 is a risk factor for frontotemporal lobar degeneration
Rollinson S, Rizzu P, Sikkink S, Baker M, Halliwell N, Snowden J, Traynor BJ, Ruano D, Cairns N, Rohrer JD, Mead S, Collinge J, Rossor M, Akay E, Guerreiro R, Rademakers R, Morrison KE, Pastor P, Alonso E, Martinez-Lage P, Graff-Radford N, Neary D, Heutink P, Mann DM, Van Swieten J, Pickering-Brown SM.
Frontotemporal lobar degeneration (FTLD) is now recognised as a common form of early onset dementia. Up to 40% of patients have a family history of disease demonstrating a large genetic component to its etiology. Linkage to chromosome 9p21 has recently been reported in families with this disorder.
We undertook a large scale two-stage linkage disequilibrium mapping approach of this region in the Manchester FTLD cohort. We identified association of ubiquitin associated protein 1 (UBAP1; OR 1.42 95% CI 1.08-1.88, P=0.013) with FTLD in this cohort and we replicated this finding in an additional two independent cohorts from the Netherlands (OR 1.33 95% CI 1.04-1.69, P=0.022), the USA (OR 1.4 95% CI 1.02-1.92, P=0.032) and a forth Spanish cohort approached significant association (OR 1.45 95% CI 0.97-2.17, P=0.064). However, we failed to replicate in a fifth cohort from London (OR 0.99 95% CI 0.72-1.37, P=0.989).
Quantitative analysis of UBAP1 mRNA extracted from tissue from the Manchester cases demonstrated a significant reduction of expression from the disease-associated haplotype. In addition, we identified a case of familial FTLD that demonstrated colocalisation of UBAP1 and TDP-43 in the neuronal cytoplasmic inclusions in the brain of this individual.
Our data for the first time identifies UBAP1 as a genetic risk factor for FTLD and suggests a mechanistic relationship between this protein and TDP-43.