|This article needs additional citations for verification. (December 2009)|
Glabellar reflex (also known as the "glabellar tap sign") (Glabella) is a primitive reflex. It is elicited by repetitive tapping on the forehead. Subjects blink in response to the first several taps. If the blinking persists, this is known as Myerson's sign and is abnormal and a sign of frontal release; it is often seen in people who have Parkinson's disease.
The afferent sensory signals are transmitted by the trigeminal nerve, and the efferent signals come back to orbicularis oculi muscle via the facial nerve, which in turn reflexively contracts causing blinking.
Parkinson's disease is a neurodegenerative disease; it causes neuronal loss in the substantia nigra, which is often diagnosed when viewing patients with abnormal responses in several components of their innate primitive reflexes, one commonly tested is known as the “glabellar tap.” In recent studies scientists have been able to use homozygosity mapping and whole exome sequencing. With this, scientists have discovered a destructive mutation in “DNAJC6” in two patients with juvenile Parkinsonism. This particular mutation is associated with uncommon transcripts and marked reduced DNAJC6 mRNA level. This particular gene encodes the HSP40 auxilin, which is a special protein that is selectively expressed in neurons and allows specificity to the ATPase movement of its partner Hcs70 in clathrin uncoating. Clathrin-coated vesicles moderate various but specific mechanisms, for example nutrient uptake, down regulation of hormone receptors, the creation of synaptic vesicles, virus entry, and transportation of biosynthetic proteins to lysosomes. The processes of this particular coating assembly and disassembly are in-built features of clathrin-mediated vesicular transport.
This particular coating assembly is important and entails recruitment of clathrin triskelia, which are adaptor groups and other determinants that impact coat assembly, cargo sequestration, membrane invagination, and scission. The coat disassembly is understood to be important for fusion of vesicles with the target membrane and for recycling of fundamental components of clathrin coats to the cytoplasm for additional cycles of vesicle construction. Scientists haven’t determined the exact process of the uncoating, so the substantial mechanism of un-coating is uncertain. There is a protein that was discovered that seems to indicate an onset of Parkinson’s disease; it’s called Sacharomyces cerevisiae J-domain protein, which is referred to as Aux1. The silencing of Aux1 has a consequence of an excess amount of clathrin-coated vesicles, debilitated cargo delivery, and a heightened amount of vesicle-associated to cytoplasmic clathrin.
The endocytic/lysosomal channel in the pathogenesis of Parkinson disease is critical in discovering cures. There is no certain genetic link to the disease yet but there have been some genes that scientists think are correlated with the disease. One gene in particular when referring to what they think is hereditary Parkinson’s Disease, scientists have discovered a gene they named SNCA that is a convincing component for predicting fast motor decline in primary Parkinson’s disease. This gene is thought to be an inherited component. The gene duplication and triplication in hereditary Parkinson’s disease have been associated to increase mRNA expression levels and to which increases the severity of Parkinson’s disease. The a-synuclein protein product is a major component. It is thought that the Lewy bodies are the proteins that are most likely to contribute the neurodegeneration and thusly to the motor symptom decline in patients. Scientists think SNCA is a promising target for therapy and could possibly intercede and benefit most patients with early onset of Parkinson’s disease. SNCA is the first study to link motor symptoms such as the glabellar tap to genes.
- "Glabellar tap". GP Notebook. Retrieved 18 April 2012.
- Ritz, Beate; Rhodes, Shannon L.; Bordelon, Yvette; Bronstein, Jeff; Lewis, Patrick (May 15, 2012). "α-Synuclein Genetic Variants Predict Faster Motor Symptom Progression in Idiopathic Parkinson Disease". PLoS ONE 7 (5): e36199. doi:10.1371/journal.pone.0036199.
- Pishvaee, Babak; Payne, Gregory S.; Costaguta, Giancarlo; Yeung, Bonny G.; Ryazantsev, Sergey; Greener, Tsvika; Greene, Lois E.; Eisenberg, Evan; McCaffery, J. Michael (14 November 2000). Nature Cell Biology 2 (12): 958–963. doi:10.1038/35046619.
- Paisán-Ruiz, Coro; Guevara, Rocio; Federoff, Monica; Hanagasi, Hasmet; Sina, Fardaz; Elahi, Elahe; Schneider, Susanne A.; Schwingenschuh, Petra; Bajaj, Nin; Emre, Murat; Singleton, Andrew B.; Hardy, John; Bhatia, Kailash P.; Brandner, Sebastian; Lees, Andrew J.; Houlden, Henry (15 September 2010). "Early-onset L-dopa-responsive parkinsonism with pyramidal signs due to ATP13A2, PLA2G6, FBXO7 and spatacsin mutations". Movement Disorders 25 (12): 1791–1800. doi:10.1002/mds.23221.
- Edvardson, Simon; Cinnamon, Yuval; Ta-Shma, Asaf; Shaag, Avraham; Yim, Yang-In; Zenvirt, Shamir; Jalas, Chaim; Lesage, Suzanne; Brice, Alexis; Taraboulos, Albert; Kaestner, Klaus H.; Greene, Lois E.; Elpeleg, Orly; Wider, Christian (May 1, 2012). "A Deleterious Mutation in DNAJC6 Encoding the Neuronal-Specific Clathrin-Uncoating Co-Chaperone Auxilin, Is Associated with Juvenile Parkinsonism". PLoS ONE 7 (5): e36458. doi:10.1371/journal.pone.0036458.