Other biofluids have been tested, such as urine, from which Simmons et al., 2021 [37] could detect higher p75NTR in HD mice compared to controls. Saliva was demonstrated to contain detectable levels of tHTT, correlating with some HD clinical measures [38] and feces was used to detect bacterial alterations related to clinical features [39]. The gene discussed is NGFR; the disease is Huntington disease.