Restless Legs Syndrome (RLS) is a common neurological disorders seen in ~10% of the US population. RLS-associated sleep deprivation can seriously impact life quality, causing anxiety, depression and attention-deficit/hyperactivity disorder (ADHD) symptoms. Moreover, RLS may portend hypertension, heart disease and stroke. RLS exhibits both familial and non-familiar (idiopathic) forms, with ~60% of cases having a family history of the disease. BTBD9 is one of the genetic risk factors, associated with decreased serum iron (Fe) level. Interestingly, lymphocytes from RLS patients have an altered Fe management protein profile, which also regulates manganese (Mn) homeostasis. This raises the question as to whether the symptoms inherent to RLS patients are the result of Fe deficiency or elevated concentrations of another metal that opportunistically increases when Fe levels are low. Here we present novel data that BTBD9 functions to regulate Mn homeostasis in Caenorhabditis elegans (C. elegans). A blast search identified
hpo-9 as the BTBD9 homolog in C. elegans, with ~75% sequence similarity. A mutant strain
tm3719 (
hpo-9-/-) carrying 761 bp deletion of
hpo-9 was obtained. We found that
hpo-9-/- worms were more sensitive to Mn exposure. Upon Mn treatment,
hpo-9-/- worms showed a significantly lower survival rate and more severe DAergic neurodegeneration compared with wild type worms. Interestingly, no difference was seen when worms were exposed to Fe. However, a low level of Fe (0.1 mM) pretreatment was able to protect Mn-induced lethality. To better characterize HPO-9 protein, a transcriptional fusion construct was created with green fluorescent protein (GFP) driven under
hpo-9 promoter. We found that GFP was present high in the head and pharynx and low in the intestine and seam cells. Using a confocal microscopy, we found that
hpo-9 was expressed in dopaminergic neurons, indicating that HPO-9 might play a role in dopamine signaling. To confirm that, we over-expressed HPO-9 in DAergic neurons of
hpo-9-/- worms and found that it rescued Mn-induced DAergic neurodegeneration. Together, our results suggest a novel role for
hpo-9/BTBD9 in regulating Mn homeostasis and possibly dopamine signaling in C. elegans.