The BSND gene provides instructions for making a protein called barttin. This protein is found primarily in the kidneys, where it attaches (binds) to two specific chloride channels: ClC-Ka (produced from the CLCNKA gene) and ClC-Kb (produced from the CLCNKB gene). The ClC-Ka and ClC-Kb channels transport charged atoms of chlorine (chloride ions) out of kidney cells.
Barttin is essential for the normal placement of ClC-Ka and ClC-Kb channels in the cell membrane. It also regulates the channels' stability and function. The transport of chloride ions is part of the mechanism by which the kidneys reabsorb salt (sodium chloride or NaCl) from the urine back into the bloodstream. The retention of salt affects the body's fluid levels and helps maintain blood pressure.
Barttin, ClC-Ka, and ClC-Kb are also found in the inner ear, where they play a role in normal hearing.
Health Conditions Related to Genetic Changes
More than a dozen mutations in the BSND gene have been identified in people with Bartter syndrome type IV. This form of the disorder causes severe or life-threatening health problems that become apparent before or soon after birth. Affected individuals also have hearing loss caused by abnormalities in the inner ear, which is why Bartter syndrome type IV is also known as antenatal Bartter syndrome with sensorineural deafness.
BSND gene mutations impair barttin's ability to regulate the ClC-Ka and ClC-Kb channels. Some mutations keep the channels from ever reaching the cell membrane. Other mutations allow the channels to reach the cell membrane but prevent them from transporting ions properly. As a result, the kidneys cannot reabsorb salt normally and excess salt is lost through the urine (salt wasting). The abnormal salt loss disrupts the normal balance of ions in the body. This imbalance underlies many of the major features of Bartter syndrome, including a failure to grow and gain weight at the expected rate (failure to thrive), dehydration, constipation, and increased urine production (polyuria). A loss of ClC-Ka and ClC-Kb function in the inner ear is responsible for the hearing loss characteristic of Bartter syndrome type IV.More About This Health Condition
Nonsyndromic hearing loss
MedlinePlus Genetics provides information about Nonsyndromic hearing lossMore About This Health Condition
Other Names for This Gene
- Bartter syndrome, infantile, with sensorineural deafness (Barttin)
- barttin CLCNK-type chloride channel accessory beta subunit
- deafness, autosomal recessive 73
Additional Information & Resources
Tests Listed in the Genetic Testing Registry
Scientific Articles on PubMed
Catalog of Genes and Diseases from OMIM
- Birkenhager R, Otto E, Schurmann MJ, Vollmer M, Ruf EM, Maier-Lutz I, Beekmann F, Fekete A, Omran H, Feldmann D, Milford DV, Jeck N, Konrad M, Landau D, Knoers NV, Antignac C, Sudbrak R, Kispert A, Hildebrandt F. Mutation of BSND causes Bartter syndrome with sensorineural deafness and kidney failure. Nat Genet. 2001 Nov;29(3):310-4. doi: 10.1038/ng752. Citation on PubMed
- Estevez R, Boettger T, Stein V, Birkenhager R, Otto E, Hildebrandt F, Jentsch TJ. Barttin is a Cl- channel beta-subunit crucial for renal Cl- reabsorption and inner ear K+ secretion. Nature. 2001 Nov 29;414(6863):558-61. doi: 10.1038/35107099. Citation on PubMed
- Hayama A, Rai T, Sasaki S, Uchida S. Molecular mechanisms of Bartter syndrome caused by mutations in the BSND gene. Histochem Cell Biol. 2003 Jun;119(6):485-93. doi: 10.1007/s00418-003-0535-2. Epub 2003 May 22. Citation on PubMed
- Janssen AG, Scholl U, Domeyer C, Nothmann D, Leinenweber A, Fahlke C. Disease-causing dysfunctions of barttin in Bartter syndrome type IV. J Am Soc Nephrol. 2009 Jan;20(1):145-53. doi: 10.1681/ASN.2008010102. Epub 2008 Sep 5. Citation on PubMed or Free article on PubMed Central
- Kramer BK, Bergler T, Stoelcker B, Waldegger S. Mechanisms of Disease: the kidney-specific chloride channels ClCKA and ClCKB, the Barttin subunit, and their clinical relevance. Nat Clin Pract Nephrol. 2008 Jan;4(1):38-46. doi: 10.1038/ncpneph0689. Citation on PubMed
- Miyamura N, Matsumoto K, Taguchi T, Tokunaga H, Nishikawa T, Nishida K, Toyonaga T, Sakakida M, Araki E. Atypical Bartter syndrome with sensorineural deafness with G47R mutation of the beta-subunit for ClC-Ka and ClC-Kb chloride channels, barttin. J Clin Endocrinol Metab. 2003 Feb;88(2):781-6. doi: 10.1210/jc.2002-021398. Citation on PubMed
- Riazuddin S, Anwar S, Fischer M, Ahmed ZM, Khan SY, Janssen AG, Zafar AU, Scholl U, Husnain T, Belyantseva IA, Friedman PL, Riazuddin S, Friedman TB, Fahlke C. Molecular basis of DFNB73: mutations of BSND can cause nonsyndromic deafness or Bartter syndrome. Am J Hum Genet. 2009 Aug;85(2):273-80. doi: 10.1016/j.ajhg.2009.07.003. Epub 2009 Jul 30. Citation on PubMed or Free article on PubMed Central
- Scholl U, Hebeisen S, Janssen AG, Muller-Newen G, Alekov A, Fahlke C. Barttin modulates trafficking and function of ClC-K channels. Proc Natl Acad Sci U S A. 2006 Jul 25;103(30):11411-6. doi: 10.1073/pnas.0601631103. Epub 2006 Jul 18. Citation on PubMed or Free article on PubMed Central