The 27kDa heat shock protein 1 (HSP27) is a member of the ubiquitously expressed small heat shock protein family and has pleiotropic cytoprotective functions. Since HSP27 may act as a motor neuron survival factor, we analyzed the genetic contribution of the human HSPB1 gene (HSPB1) to the etiology of amyotrophic lateral sclerosis (ALS). In a cohort of sporadic ALS patients, we identified three rare genetic variations and one of which (c.-217T>C) targeted a conserved nucleotide of the Heat Shock Element (HSE) in the HSPB1 promoter. Since binding of Heat Shock Factor 1 (HSF1) to this HSE is essential for stressinduced transcription of HSPB1, we examined the effect of the c.-217C allele on transcriptional activity and HSF binding. The basal promoter activity of the HSPB1 c.-217C mutant allele decreased to 50% as compared to the wild-type promoter in neuronal and nonneuronal cells. Following heat shock, the HSE variant attenuated significantly the stressrelated increase in transcription. Electrophoretic mobility shift assays demonstrated a dramatically reduced HSF-binding to the c.-217C mutant allele as compared to the c.-217T wild-type allele. In conclusion, our study underscores the importance of the c.-217T nucleotide for HSF binding and heat inducibility of HSPB1. Therefore, our study suggests that the functional HSPB1 variant may represent a genetic modifier in the pathogenesis of motor neuron disease; however, it is necessary to confirm this HSPB1 variant in additional ALS patients. are likely multifactorial processes, including oxidative damage, aggregation, excitotoxicity, inflammation and neurofilament disorganization (Bruijn et al., 2004;Pasinelli and Brown, 2006). Some of these pathogenic processes are known to act as stress stimuli and induce a cellular heat shock response through stress-induced transcription of heat shock proteins (HSPs). Therefore an upregulation of HSPs is seen in several neuronal diseases including ALS (Vleminckx et al., 2002;Bidmon et al., 2004). These HSPs function as molecular chaperones in assisting the correct folding of denatured proteins and by inhibiting cell death pathways. The heat shock 27kDa protein 1 (HSP27: gene symbol HSPB1; MIM# 602195), is a member of the small heat shock protein family and is constitutively expressed in motor neurons (Plumier et al., 1997). Motor neurons upregulate the expression of HSP27 after peripheral nerve transection and this induction is crucial for their survival (Costigan et al., 1998;Benn et al., 2002;Kalmar et al., 2002). There is also increasing evidence for the neuroprotective capacities of HSP27 overexpression; e.g. simultaneous exogenous delivery of HSP27 and HSP70 (gene symbol HSPA1A) protects against copper-zinc superoxide dismutase 1 (SOD1)-mutant induced cell death in mammalian neuronal cells (Bruening et al., 1999;Wagstaff et al., 1999;Wyttenbach et al., 2002;Patel et al., 2005;Batulan et al., 2006), although overexpression of HSP27 alone is insufficient to obtain protection against the toxicity of mutant SOD1 . Furthermore, incr...