C9orf72 and frontotemporal dementia: Also, research has shown that in the frontal cortex alone, thousands of genes are differentially expressed in C9orf72 HRE carrier ALS-FTD patients versus ALS-FTD patients without C9orf72 HRE (Dickson et al., 2019), and distinct expression patterns were evident in C9orf72 HRE carriers compared to healthy controls.