C9orf72 and brain injury: In particular, some forms of FTD and ALS share the pathological substrate, the transactive DNA-binding protein 43 (TDP-43) and the C9ORF72 gene [59,60], as well as some environmental risk factors including agricultural chemicals and professional sports involving high risk of mild traumatic brain injuries such as concussion and subconcussion [38], leading to a pro-oxidative state and consequent neuron degeneration and astrocyte dysfunction [25,61,62].