A Rostrocaudal Muscular Dystrophy Caused by a Defect in Choline Kinase Beta, the First Enzyme in Phosphatidylcholine Biosynthesis

Muscular dystrophies include a diverse group of genetically heterogeneous disorders that together affect 1 in 2000 births worldwide. The diseases are characterized by progressive muscle weakness and wasting that lead to severe disability and often premature death. Rostrocaudal muscular dystrophy (rmd) is a new recessive mouse mutation that causes a rapidly progressive muscular dystrophy and a neonatal forelimb bone deformity. The rmd mutation is a 1.6-kb intragenic deletion within the choline kinase beta (Chkb) gene, resulting in a complete loss of CHKB protein and enzymatic activity. CHKB is one of two mammalian choline kinase (CHK) enzymes (α and β) that catalyze the phosphorylation of choline to phosphocholine in the biosynthesis of the major membrane phospholipid phosphatidylcholine. While mutant rmd mice show a dramatic decrease of CHK activity in all tissues, the dystrophy is only evident in skeletal muscle tissues in an unusual rostral-to-caudal gradient. Minor membrane disruption similar to dysferlinopathies suggest that membrane fusion defects may underlie this dystrophy, because severe membrane disruptions are not evident as determined by creatine kinase levels, Evans Blue infiltration, and unaltered levels of proteins in the dystrophin-glycoprotein complex. The rmd mutant mouse offers the first demonstration of a defect in a phospholipid biosynthetic enzyme causing muscular dystrophy, representing a unique model for understanding mechanisms of muscle degeneration. Muscular dystrophies include a diverse group of genetically heterogeneous disorders that together affect 1 in 2000 births worldwide. The diseases are characterized by progressive muscle weakness and wasting that lead to severe disability and often premature death. Rostrocaudal muscular dystrophy (rmd) is a new recessive mouse mutation that causes a rapidly progressive muscular dystrophy and a neonatal forelimb bone deformity. The rmd mutation is a 1.6-kb intragenic deletion within the choline kinase beta (Chkb) gene, resulting in a complete loss of CHKB protein and enzymatic activity. CHKB is one of two mammalian choline kinase (CHK) enzymes (α and β) that catalyze the phosphorylation of choline to phosphocholine in the biosynthesis of the major membrane phospholipid phosphatidylcholine. While mutant rmd mice show a dramatic decrease of CHK activity in all tissues, the dystrophy is only evident in skeletal muscle tissues in an unusual rostral-to-caudal gradient. Minor membrane disruption similar to dysferlinopathies suggest that membrane fusion defects may underlie this dystrophy, because severe membrane disruptions are not evident as determined by creatine kinase levels, Evans Blue infiltration, and unaltered levels of proteins in the dystrophin-glycoprotein complex. The rmd mutant mouse offers the first demonstration of a defect in a phospholipid biosynthetic enzyme causing muscular dystrophy, representing a unique model for understanding mechanisms of muscle degeneration. Muscular dystrophies are a variable class of more than 20 human disorders characterized by progressive muscle wasting and weakness resulting from myofiber degeneration and regeneration. Histologically, variation in myofiber size with centrally localized nuclei, fibrosis, and fatty infiltration are common features (1O'Brien K.F. Kunkel L.M. Mol. Genet. Metab. 2001; 74: 75-88Crossref PubMed Scopus (88) Google Scholar, 2Emery A.E.H. Neuromuscul. Disord. 2002; 12: 343-349Abstract Full Text Full Text PDF PubMed Scopus (95) Google Scholar). Despite their common pathologies, the genetic causes, severity, age of onset, and inheritance patterns vary widely among the dystrophies. The Muscular Dystrophy Association currently lists over 40 neuromuscular diseases as targets for its research programs and categorizes them by phenotypic characteristics such as age of onset, affected muscle groups, and inheritance pattern (Muscular Dystrophy Association, www.mdausa.org). In the last 10 years, the genetic mapping and identification of novel skeletal muscle genes, including cytoskeletal, cytosolic, nuclear membrane, sarcolemmal and extracellular matrix proteins, has dramatically changed this phenotype-based classification and provided clues as to the molecular basis of these disorders (3Cohn R.D. Campbell K.P. Muscle Nerve. 2000; 23: 1456-1471Crossref PubMed Scopus (424) Google Scholar). What was once considered a single disease entity such as limb-girdle muscular dystrophy (LGMD) 4The abbreviations used are: LGMD, limb-girdle muscular dystrophy; B6, C57BL/6J; CHK, choline kinase; Chkb, choline kinase β; Chka, choline kinase α; CK, creatine kinase; COX, cytochrome-c oxidase; CPT, CDP-choline:1,2-diacylglycerol cholinephosphotransferase; Cpt1b, carnitine palmitoyltransferase type 1b; DGC, dystrophin-glycoprotein complex; EBD, Evans Blue dye; H&E, hematoxylin and eosin; PC, phosphatidylcholine; PE, phosphatidylethanolamine; rmd, rostrocaudal muscular dystrophy. has now been subdivided into seven different molecularly defined autosomal dominant (LGMD1A–1G) and ten autosomal recessive (LGMD2A–2J) diseases. Not surprisingly, many of these genes have converged to define pathways critical for the normal functioning and maintenance of skeletal muscles. The fact that many muscular dystrophy cases exist in which mutations to known dystrophy-causing genes have not been detected suggests that this discovery period in human and model organism genetics will continue to identify novel disease genes and mechanisms. The most common forms of muscular dystrophy result from mutations in genes coding for sarcolemmal and extracellular matrix proteins in the dystrophin-glycoprotein complex (DGC) (4Ervasti J.M. Ohlendieck K. Kahl S.D. Gaver M.G. Campbell K.P. Nature. 1990; 345: 315-319Crossref PubMed Scopus (820) Google Scholar), which acts as a linker between the cytoskeleton of the muscle cell and the extracellular matrix, thus providing mechanical support to the plasma membrane during myofiber contraction (5Michele D.E. Campbell K.P. J. Biol. Chem. 2003; 278: 15457-15460Abstract Full Text Full Text PDF PubMed Scopus (375) Google Scholar). The association of a large number of muscular dystrophies with the DGC reflects the need to maintain the structural integrity of the plasma membrane of skeletal muscle. Disruption of DGC components results in a loss of membrane stability and subsequent degeneration of muscle fibers (3Cohn R.D. Campbell K.P. Muscle Nerve. 2000; 23: 1456-1471Crossref PubMed Scopus (424) Google Scholar). Recently, defects in post-translational glycosylation of membrane proteins have been shown to be causative factors in muscle-eye-brain disease, Fukuyama congenital muscular dystrophy, Walker-Warburg syndrome, congenital muscular dystrophy type 1C, and limb-girdle muscular dystrophy type 2I (6Michele D.E. Barresi R. Kanagawa M. Saito F. Cohn R.D. Satz J.S. Dollar J. Nishino I. Kelley R.I. Somer H. Straub V. Mathews K.D. Moore S.A. Campbell K.P. Nature. 2002; 418: 417-422Crossref PubMed Scopus (692) Google Scholar, 7Grewal P.K. Hewitt J.E. Hum. Mol. Genet. 2003; 12: R259-R264Crossref PubMed Scopus (95) Google Scholar, 8Balci B. Uyanik G. Dincer P. Gross C. Willer T. Talim B. Haliloglu G. Kale G. Hehr U. Winkler J. Topaloglu H. Neuromuscul. Disord. 2005; 15: 271-275Abstract Full Text Full Text PDF PubMed Scopus (149) Google Scholar). In most mammalian tissues, plasma membrane disruption is a common form of injury due to mechanical stress, and resealing of the damaged membrane is critical for cell survival (9McNeil P.L. Miyake K. Vogel S.S. Proc. Natl. Acad. Sci. U. S. A. 2003; 100: 4592-4597Crossref PubMed Scopus (106) Google Scholar, 10McNeil P.L. Steinhardt R.A. Annu. Rev. Cell Dev. Biol. 2003; 19: 697-731Crossref PubMed Scopus (375) Google Scholar). In skeletal muscle, disruptions of the membrane are more frequent due to the repeated lengthening and shortening of muscle cells during contraction (11Hayashi Y.K. Lancet. 2003; 362: 843-844Abstract Full Text Full Text PDF PubMed Scopus (7) Google Scholar). Defects in the dysferlin gene result in limb-girdle muscular dystrophy type 2B (LGMD2B) and its allelic disease Miyoshi myopathy (12Liu J. Aoki M. Illa I. Wu C. Fardeau M. Angelini C. Serrano C. Urtizberea J.A. Hentati F. Hamida M.B. Bohlega S. Culper E.J. Amato A.A. Bossie K. Oeltjen J. Bejaoui K. McKenna-Yasek D. Hosler B.A. Schurr E. Arahata K. de Jong P.J. Brown Jr., R.H. Nat. Genet. 1998; 20: 31-36Crossref PubMed Scopus (758) Google Scholar) through alterations in repair-vesicle fusion with the phospholipid membrane, resulting in necrosis of muscle fibers in both humans (13Bansal D. Campbell K.P. Trends Cell Biol. 2004; 14: 206-213Abstract Full Text Full Text PDF PubMed Scopus (243) Google Scholar) and mice (14Ho M. Post C.M. Donahue L.R. Lidov H.G. Bronson R.T. Goolsby H. Watkins S.C. Cox G.A. Brown Jr., R.H. Hum. Mol. Genet. 2004; 13: 1999-2010Crossref PubMed Scopus (158) Google Scholar). We have identified a new spontaneous recessive mouse mutation that leads to a progressive muscular dystrophy with a rostral-to-caudal gradient of severity (rmd, rostrocaudal muscular dystrophy) and a neonatal forelimb bone deformity. By positional cloning we have identified the molecular defect in rmd mutant mice as an intragenic deletion in the choline kinase beta (Chkb) gene, one of two mammalian choline kinase (CHK) enzymes (α and β). The monomeric CHK proteins combine to form the homoor hetero-dimeric forms C. H. K. 2004; PubMed Scopus Google Scholar) that catalyze the phosphorylation of choline to phosphocholine in the first in the for the biosynthesis of K. PubMed Scopus Google Scholar). is the major phospholipid of the plasma membrane J. 2003; Full Text Full Text PDF PubMed Scopus Google Scholar), an for many M. 2002; PubMed Scopus Google Scholar), and is to be for mammalian survival D.E. J. Biol. Chem. 1998; Full Text Full Text PDF PubMed Scopus Google Scholar, D.E. Cell Biol. 1990; PubMed Scopus Google Scholar). The biosynthetic of CHK, may be an in cell and PubMed Scopus Google Scholar). The rmd mouse offers the first demonstration that a defect in a phospholipid biosynthetic enzyme muscular dystrophy, that membrane as as proteins are critical to the disease rmd mice phenotypic features with mouse that have a defect in and are a model for human limb-girdle muscular dystrophy 2B discovery of a mouse mutation in will into the phospholipid biosynthetic pathways for the and maintenance of muscle of a and rmd mutation in an between mice and mice in a mapping for an mutation Hum. Mol. Genet. 2003; 12: PubMed Scopus Google Scholar). mapping was between the affected mutant and The affected mice to and the rmd was by the of an into a severe The was with a resulting in which for in positional cloning and of the resulting mapping with was in the mouse with two mice and with and in and by hematoxylin and of and forelimb muscle with of and muscle from and and mice as with and in mouse was in 20 fibers in a with and and a and of and mice to the of H. PubMed Google Scholar), bone is and is mice for in in for and with of 1 of of and of which to a was and to and muscle from and mice and in and with a for and of fusion the In a of and mice with and in and as and 40 with Evans Blue 10 in of with two mice model of and one to show infiltration of into muscle as a and and for of of muscle in in in and by for into muscle from the Evans Blue membrane integrity in dysferlin for in for 1 in in of mouse in for 1 with of for and as from and mice and and and was for muscle from and in in in with normal with for 1 by with was as and from 1 of muscle from and from 10 of forelimb and muscle, and from and with a 10 and of the and for we for gene an to of and and the of and The was the mouse protein was from of from and and tissues and with for an in the the of and muscle from and mice 40 and in to a in a and in of including 1 of 10 of for and for of the was determined by the R. Moore J.A. K. in Scholar) of protein from with for and was into gradient and for V. to by with mouse to and and with with and in rmd and and in from and and for choline kinase activity and phospholipid tissues in of 20 and 1 of with a and The CHK activity was determined as K. PubMed Scopus Google Scholar) with The in a of that 10 and for The was the activity of CHK with an fusion proteins with protein and the was used for CHK C. A. K. J. 2002; PubMed Scopus Google Scholar). of the of and in and in of of plasma was with for as an and the of and determined by A. S. PubMed Scopus Google Scholar). of and in was as an to of from by the of J. M. J. Biol. Chem. Full Text PDF PubMed Google Scholar), and and by the of with R. B. J.E. J. Biol. Chem. 2002; Full Text Full Text PDF PubMed Scopus Google Scholar). with of for and Scholar), and considered different and of rmd spontaneous recessive rmd, resulting in a weakness and muscle wasting disease, was identified The The disease of mice is first with mutant mice than their and an of the that results from bone of severe of the and bone not to be the disease the and rmd mice by of age as by of The forelimb show only degeneration the forelimb bone and the mice are to and of the forelimb skeletal muscle loss of muscle fibers by variation in and nuclei, of of muscle are and skeletal muscle, by of severe muscular dystrophy, including nuclei, fatty infiltration, and loss of muscle fibers and The disease is in the and 1 of forelimb continue to show only defects with loss of muscle fibers and are affected 1 of age and The of fibers with in muscle tissues from 1 of age to by that The size of fibers was in than in and the variation in size was not different The muscle degeneration not to affect because mice have of is in and have been in the neuromuscular not that rmd is not a model for diseases. In and muscular the loss of the protein the dystrophin-glycoprotein resulting in to the sarcolemmal membrane E. and A.E.H. Scholar). similar membrane in the rmd dystrophy, we used Evans a molecular that not the into normal skeletal muscle fibers will into muscle fibers of a number of with sarcolemmal including a model for muscular dystrophy V. J.A. J.S. Campbell K.P. J. Cell Biol. PubMed Scopus (424) Google Scholar). skeletal muscle from mice in we that skeletal muscle from both the of of by in and only single fibers in In in of suggest that the defect not lead to to the sarcolemmal membrane and of normal membrane may be In a of muscular alterations loss of protein components of the sarcolemmal membrane, membrane are We the levels of membrane proteins by of protein from and of and mice with to and of these proteins in their of between and not In muscle of both and normal of dysferlin and the that the rmd dystrophy is to be by of dysferlin of of the DGC sarcolemmal complex of In muscular levels of creatine kinase as the enzyme is from tissues during muscle is most evident in mice with sarcolemmal membrane levels of plasma are In muscle fibers from mice show only levels which causes levels in mice to dramatically D. Miyake K. Vogel S.S. S. R. P.L. Campbell K.P. Nature. 2003; PubMed Scopus Google Scholar). from and mutant rmd mice levels with levels, and membrane integrity results rmd mice a progressive muscular dystrophy, sarcolemmal integrity not to be a for the dystrophy. of muscle fibers in muscular dystrophies are and including alterations in the of the B. K. C. I. G. P. J. Hum. Genet. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar), we for in and was of in both and forelimb which be of may be a to muscle degeneration. The of has been as a to and in many diseases syndrome, disease, and B. M. M. 2002; PubMed Scopus Google Scholar, B. Acad. Sci. PubMed Google Scholar), and widely in skeletal of not in and that the of was not a result of a we cytochrome-c complex of the of muscle in muscle fibers has been to be of defects alterations in of the result in of F. G. Hum. Mol. Genet. 2002; PubMed Scopus Google Scholar). We between and in not which suggests that a defect is not for the dystrophy. rmd, a 1.6-kb in rmd mutation was to the of between and We a genetic and through of the rmd a of and which the genetic to a known genes the gene was to a with known human mouse neuromuscular that rmd was a novel muscular dystrophy genes within the for variation in rmd with and The only mutation identified in the genetic was a intragenic deletion within the gene that the of through the first of We have through of that the is to in and into 10 results in a that for novel the the protein within 10 and the the protein only the be and choline and the be with an that CHKB protein protein is in tissues not is protein detected by and of CHK activity kinase activity in tissues from and CHK molecular forms from is that activity not by was due to activity not by was due to and that the activity was from of muscle with membrane defects of disruption with of D. Miyake K. Vogel S.S. S. R. P.L. Campbell K.P. Nature. 2003; PubMed Scopus Google Scholar). the of in membrane phospholipid we that alterations in sarcolemmal may exist in skeletal muscle. we of sarcolemmal and of in as with the in and similar to by D. Miyake K. Vogel S.S. S. R. P.L. Campbell K.P. Nature. 2003; PubMed Scopus Google Scholar). We of disruption in which not in and and in CHK enzymatic activity in to mice was in and mice as with in both the and of CHK activity was The results of CHK that all CHK activity in mice from the CHK the first of the major for we the decrease in CHK activity phospholipid in rmd CHK activity was in was in the of in and as by and a decrease in levels in muscle from forelimb and a levels in was in mice as with in levels in forelimb that phospholipid is not in the rmd the is to in the in both forelimb and the of as with levels may suggest that in the levels of in the by are to the of in mouse CHK activity was in the which the has been shown to of we and in the plasma and as of plasma and between and mice in levels of plasma and plasma not between and mice between and mice for levels of plasma may that the loss of one of in results in a of and pathways in plasma that are not for in mammalian through the of by is not in tissues D.E. Cell Biol. 1990; PubMed Scopus Google Scholar, L.R. Bronson R. D.E. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar) and may the unaltered of these in the and levels in and mice levels by of for plasma and for for all are are different from by of are different from by of are different from by of are different from by of are different from by of in a new and is from the gene Cpt1b, which is the muscle of the first enzyme in the of fatty to Cox B. T. P. J. Biol. Chem. 2002; Full Text Full Text PDF PubMed Scopus Google Scholar). of the of and Cpt1b, and the of from both genes, have the for between these two genes, including within T. H. J. 2003; PubMed Scopus Google Scholar, C. H. K. J. 2000; Full Text Full Text PDF PubMed Google Scholar, K. M. H. J. Biol. Chem. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar). We a of a in tissues by not was with which a in in muscle as with the protein as an and of in muscle as with we have the of the with for all and In of enzymatic activity of activity of as J. P. J. B. J. Biol. Chem. 1998; Full Text Full Text PDF PubMed Scopus Google in between and We have in tissues to the decrease in tissues was a due to muscle degeneration and in in as with that of is not a of muscular dystrophies is to enzymatic activity in is not affected and is not in the rmd dystrophy The phospholipid that mammalian cells of major phospholipid and which are between two The and are in the extracellular the and are in the membrane this vary with type Chem. 2005; 13: PubMed Scopus Google Scholar). Disruption of the of results in major defects in A. S. Mol. Biol. 2001; PubMed Google Scholar). in have been in muscle of the mouse model of congenital muscular dystrophy) and in human muscular dystrophy F. G. M. D. PubMed Scopus (7) Google Scholar, U. S. C. 2003; PubMed Scopus Google Scholar) and U. S. C. 2003; PubMed Scopus Google Scholar) as with normal the of in membrane stability of muscle for membrane has been in cell G. F. T. J. Full Text PDF PubMed Google Scholar) and disease J.S. J. Full Text PDF PubMed Google Scholar). has been that of membrane may be a to the of sarcolemmal in normal Mol. PubMed Scopus Google Scholar), and alterations in the of membrane result in muscle has been shown that disruption of leads to membrane phospholipid through an of its with the phospholipid pathways in muscular dystrophy muscle fibers Mol. PubMed Scopus Google Scholar). to between the DGC complex and phospholipid components of the membrane M. A. G. M. P. G. Muscle Nerve. PubMed Scopus Google Scholar, E. S. F. C. M. J. A. J. Biol. Chem. 2003; 278: Full Text Full Text PDF PubMed Scopus Google Scholar, J.E. Cell Biol. PubMed Scopus Google Scholar). we the first of a genetic Chkb, in a membrane phospholipid biosynthetic resulting in muscular dystrophy. In we show that this dystrophy is not by the loss of membrane proteins, providing for a unique of membrane in muscle in the and of in plasma may have the of proteins and of the stability and of localized membrane R. 2004; PubMed Scopus Google Scholar). the between membrane is the for the fusion Scopus Google Scholar), and alterations in the of have been to membrane and the for to with the membrane H. Scopus Google Scholar). membrane disruption due to mechanical is common in mammalian tissues, and in skeletal muscle, disruptions of the membrane are more frequent due to injury (11Hayashi Y.K. Lancet. 2003; 362: 843-844Abstract Full Text Full Text PDF PubMed Scopus (7) Google Scholar). of damaged by fusion with is critical for cell survival (9McNeil P.L. Miyake K. Vogel S.S. Proc. Natl. Acad. Sci. U. S. A. 2003; 100: 4592-4597Crossref PubMed Scopus (106) Google Scholar, 10McNeil P.L. Steinhardt R.A. Annu. Rev. Cell Dev. Biol. 2003; 19: 697-731Crossref PubMed Scopus (375) Google Scholar). We have disruptions in the of muscle by with an of large of similar to in muscular dystrophies. levels in the rmd mouse are not that these features are not due to loss of dysferlin may be a of membrane The of between membrane is a and a loss of lead to disruptions in pathways J.M. Rev. 2002; PubMed Scopus Google Scholar) with alterations in membrane stability S. Proc. Natl. Acad. Sci. U. S. A. 2002; PubMed Scopus Google Scholar). is by a of in the membrane, with to the be by is in and which and are by J. I. M. M. E. D. PubMed Scopus Google Scholar, E. Proc. Natl. Acad. Sci. U. S. A. 1998; PubMed Scopus Google Scholar). of the of the leads to cell and subsequent M. 2002; PubMed Scopus Google Scholar, A. S. Mol. Biol. 2001; PubMed Google Scholar). in which cells to is to the of and fusion the of to more to J. Cell Biol. 2005; PubMed Scopus Google Scholar). in have been in during the of K. T. J. M. J. T. Mol. PubMed Scopus Google Scholar), which may the of in muscle. We have for of in muscle muscle and have of not that the muscle degeneration in the rmd mouse is not due to the has been that CHK activity a in the of the and CHK has been to be in K. PubMed Scopus Google Scholar). of mutant cells that CHK is of the for the and pathways that the levels of M. M. A. J. Biol. Chem. Full Text PDF PubMed Google Scholar). The loss of CHK activity may result in a of the mutant gene, which may the of the The of the gene may with the of the gene the through between the two genes, of into the loss of a in the intragenic the in is not in enzymatic and is to be in the of this muscular dystrophy In the mouse the activity of CHK are in the mouse are C. A. K. J. 2002; PubMed Scopus Google Scholar). We have CHK activity in all tissues in rmd and alterations in levels of and are only in skeletal the of the in normal muscle. The pattern of levels and with the in rmd tissues, with and in and dystrophy in and severe alterations with severe dystrophy in results in this mouse model of muscular dystrophy, that is a of tissues to for the loss of the through biosynthesis through we of in tissues and by that the is not through an in activity. By understanding the pattern of CHKB and and their in phospholipid their in the in muscular dystrophy be is that choline kinase is an enzyme for many because alterations defects have been to A. de A. M. D. J. 2005; Google Scholar) and to and P. D.E. 2005; PubMed Scopus Google Scholar). the first that of CHK and alterations in phospholipid levels, result in muscular of levels in tissues as to by of in and to protein for all tissues by are in a new We and for critical of the for with and and for with for with neuromuscular for with for of the rmd for with and and for

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