Cilia contribute to human sense of touch
A rare and complex genetic disorder has provided Hopkins researchers with an unprecedented glimpse into how we sense temperature and texture. Writing in Proceedings of the National Academy of Sciences, the team, led by Nicholas Katsanis at the School of Medicine, identified the primary cilium, a feature of nearly all cells, as playing a critical role.
The disease in question is Bardet-Biedl syndrome (BBS), which is caused by an inherited genetic mutation. The complex nature of BBS has puzzled physicians and researchers since it was first described in 1866.
People with BBS manifest a broad range of symptoms, most of which involve a reduction or loss of sensation. Blindess and anosmia (loss of smell) are common, as are many seemingly unrelated features, such as obesity, mental retardation and kidney disease.
Recent research has focused on defects of non-motile cilia, organelles usually associated with sensory function. Non-motile cilia - as their name suggests - lack the locomotor abilities of motile cilia, such as those found in the trachea and lungs. Instead, they tend to be specialized for receiving a specific environmental stimulus.
For example, the outer segments of retinal photoreceptors - which contain light-absorbing pigments - are modified non-motile cilia, as are the aroma-detecting parts of the olfactory cells in the nose.
In BBS, mutations in two genes, Bbs1 and Bbs4, have been implicated in the malfunction of non-motile cilia. Normal copies of the two genes usually produce proteins found primarily in cilia.
While the link between genetic mutation and malfunction in vision, smell and hearing has been well-established, other sensory neurons exist whose cilia are not as visibly important to their function.
Most other cells in the body possess another kind of non-motile cilium called the primary cilium. Long thought to be useless evolutionary leftovers, primary cilia have only come into the spotlight within the last few years.
The disease in question is Bardet-Biedl syndrome (BBS), which is caused by an inherited genetic mutation. The complex nature of BBS has puzzled physicians and researchers since it was first described in 1866.
People with BBS manifest a broad range of symptoms, most of which involve a reduction or loss of sensation. Blindess and anosmia (loss of smell) are common, as are many seemingly unrelated features, such as obesity, mental retardation and kidney disease.
Recent research has focused on defects of non-motile cilia, organelles usually associated with sensory function. Non-motile cilia - as their name suggests - lack the locomotor abilities of motile cilia, such as those found in the trachea and lungs. Instead, they tend to be specialized for receiving a specific environmental stimulus.
For example, the outer segments of retinal photoreceptors - which contain light-absorbing pigments - are modified non-motile cilia, as are the aroma-detecting parts of the olfactory cells in the nose.
In BBS, mutations in two genes, Bbs1 and Bbs4, have been implicated in the malfunction of non-motile cilia. Normal copies of the two genes usually produce proteins found primarily in cilia.
While the link between genetic mutation and malfunction in vision, smell and hearing has been well-established, other sensory neurons exist whose cilia are not as visibly important to their function.
Most other cells in the body possess another kind of non-motile cilium called the primary cilium. Long thought to be useless evolutionary leftovers, primary cilia have only come into the spotlight within the last few years.
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