C5AR1 and amyotrophic lateral sclerosis: However, as this study utilised full knockout of C5aR1 in all tissues, future investigation using conditional knockout mice [30] or bone-marrow chimeras [31] to delete C5aR1 either peripherally or centrally, could help us and fellow researchers determine if C5a-C5aR1 signalling in the CNS or TA muscle (or both) affects ALS disease progression.