Aberrant Expression of Dynein light chain 1 (DYNLT1) is Associated with Human Male Factor Infertility*

Abstract

DYNLT1 is a member of a gene family identified within the t-complex of the mouse, which has been linked with male germ cell development and function in the mouse and the fly. Though defects in the expression of this gene are associated with male sterility in both these models, there has been no study examining its association with spermatogenic defects in human males. In this study, we evaluated the levels of DYNLT1 and its expression product in the germ cells of fertile human males and males suffering from spermatogenic defects. We screened fertile (n = 14), asthenozoospermic (n = 15), oligozoospermic (n = 20) and teratozoospermic (n = 23) males using PCR and Western blot analysis. Semiquantitative PCR indicated either undetectable or significantly lower levels of expression of DYNLT1 in the germ cells from several patients from across the three infertility syndrome groups, when compared with that of fertile controls. DYNLT1 was localized on head, mid-piece, and tail segments of spermatozoa from fertile males. Spermatozoa from infertile males presented either a total absence of DYNLT1 or its absence in the tail region. Majority of the infertile individuals showed negligible levels of localization of DYNLT1 on the spermatozoa. Overexpression of DYNLT1 in GC1-spg cell line resulted in the up-regulation of several cytoskeletal proteins and molecular chaperones involved in cell cycle regulation. Defective expression of DYNLT1 was associated with male factor infertility syndromes in our study population. Proteome level changes in GC1-spg cells overexpressing DYNLT1 were suggestive of its possible function in germ cell development. We have discussed the implications of these observations in the light of the known functions of DYNLT1, which included protein trafficking, membrane vesiculation, cell cycle regulation, and stem cell differentiation. DYNLT1 is a member of a gene family identified within the t-complex of the mouse, which has been linked with male germ cell development and function in the mouse and the fly. Though defects in the expression of this gene are associated with male sterility in both these models, there has been no study examining its association with spermatogenic defects in human males. In this study, we evaluated the levels of DYNLT1 and its expression product in the germ cells of fertile human males and males suffering from spermatogenic defects. We screened fertile (n = 14), asthenozoospermic (n = 15), oligozoospermic (n = 20) and teratozoospermic (n = 23) males using PCR and Western blot analysis. Semiquantitative PCR indicated either undetectable or significantly lower levels of expression of DYNLT1 in the germ cells from several patients from across the three infertility syndrome groups, when compared with that of fertile controls. DYNLT1 was localized on head, mid-piece, and tail segments of spermatozoa from fertile males. Spermatozoa from infertile males presented either a total absence of DYNLT1 or its absence in the tail region. Majority of the infertile individuals showed negligible levels of localization of DYNLT1 on the spermatozoa. Overexpression of DYNLT1 in GC1-spg cell line resulted in the up-regulation of several cytoskeletal proteins and molecular chaperones involved in cell cycle regulation. Defective expression of DYNLT1 was associated with male factor infertility syndromes in our study population. Proteome level changes in GC1-spg cells overexpressing DYNLT1 were suggestive of its possible function in germ cell development. We have discussed the implications of these observations in the light of the known functions of DYNLT1, which included protein trafficking, membrane vesiculation, cell cycle regulation, and stem cell differentiation. The t-complex of the mouse occupies the proximal half of chromosome 17 and contains genes which have profound effects on spermatogenesis. Multiple mutations in several loci in the t-complex appear to interact to cause complete male sterility (1.Lader E. Ha H.S. O'Neill M. Artzt K. Bennett D. tctex-1: a candidate gene family for a mouse t complex sterility locus.Cell. 1989; 58: 969-979Abstract Full Text PDF PubMed Google Scholar, 2.Ha H. Howard C.A. Yeom Y.I. Abe K. Uehara H. Artzt K. Bennett D. Several testis-expressed genes in the mouse t-complex have expression differences between wild-type and t-mutant mice.Dev. Genet. 1991; 12: 318-332Crossref PubMed Scopus (41) Google Scholar). Tctex-1 (t-complex testis expressed-1), lately renamed as dynein light chain 1 (Dynlt1) 1The abbreviations used are:Dynlt1dynein light chain 1DMEMDulbecco's Modified Eagles MediumBACbacterial artificial chromosome. 1The abbreviations used are:Dynlt1dynein light chain 1DMEMDulbecco's Modified Eagles MediumBACbacterial artificial chromosome., is identified as a candidate gene involved in male sterility in mice (1.Lader E. Ha H.S. O'Neill M. Artzt K. Bennett D. tctex-1: a candidate gene family for a mouse t complex sterility locus.Cell. 1989; 58: 969-979Abstract Full Text PDF PubMed Google Scholar) and maps to the t-complex in mice (3.Lyon M.F. Transmission ratio distortion in mice.Annu. Rev. Genet. 2003; 37: 393-408Crossref PubMed Scopus (132) Google Scholar). Dynlt1 is a member of a multigene family which is virtually germ cell-specific and is eightfold over expressed in t-homozygotes and 200-fold higher in testis than in other adult tissues (1.Lader E. Ha H.S. O'Neill M. Artzt K. Bennett D. tctex-1: a candidate gene family for a mouse t complex sterility locus.Cell. 1989; 58: 969-979Abstract Full Text PDF PubMed Google Scholar). The human homologue of the mouse Dynlt1 is located on chromosome 6q25.2–25.3. The amino acid sequence shows a high degree of similarity to the predicted product of the Dynlt1 gene of the mouse t complex (4.Roux A.F. Rommens J. McDowell C. Anson-Cartwright L. Bell S. Schappert K. Fishman G.A. Musarella M. Identification of a gene from Xp21 with similarity to the tctex-1 gene of the murine t complex.Hum. Mol. Genet. 1994; 3: 257-263Crossref PubMed Scopus (48) Google Scholar). dynein light chain 1 Dulbecco's Modified Eagles Medium bacterial artificial chromosome. dynein light chain 1 Dulbecco's Modified Eagles Medium bacterial artificial chromosome. DYNLT1 gene encodes a 14 kDa protein constituting the inner arm L1 of cytoplasmic and flagellar dynein complexes (5.Harrison A. Olds-Clarke P. King S.M. Identification of the t complex-encoded cytoplasmic dynein light chain tctex1 in inner arm I1 supports the involvement of flagellar dyneins in meiotic drive.J. Cell Biol. 1998; 140: 1137-1147Crossref PubMed Scopus (118) Google Scholar, 6.King S.M. Dillman III, J.F. Benashski S.E. Lye R.J. Patel-King R.S. Pfister K.K. The mouse t-complex-encoded protein Tctex-1 is a light chain of brain cytoplasmic dynein.J. Biol. Chem. 1996; 271: 32281-32287Abstract Full Text Full Text PDF PubMed Scopus (127) Google Scholar). DYNLT1 is localized to Golgi complexes as well (7.Tai A.W. Chuang J.Z. Sung C.H. Localization of Tctex-1, a cytoplasmic dynein light chain, to the Golgi apparatus and evidence for dynein complex heterogeneity.J. Biol. Chem. 1998; 273: 19639-19649Abstract Full Text Full Text PDF PubMed Scopus (69) Google Scholar). DYNLT1 protein is present in sperm tails and oocytes (8.Campbell K.S. Cooper S. Dessing M. Yates S. Buder A. Interaction of p59fyn kinase with the dynein light chain, Tctex-1, and colocalization during cytokinesis.J. Immunol. 1998; 161: 1728-1737PubMed Google Scholar, 9.O'Neill M.J. Artzt K. Identification of a germ-cell-specific transcriptional repressor in the promoter of Tctex-1.Development. 1995; 121: 561-568PubMed Google Scholar). A wide range of cellular events are brought about by cytoplasmic dynein and its association with the accessory intermediate, light intermediate, and light chain subunits. These subunits define the interaction of cytoplasmic dynein motor complex with other molecules (10.Li M.G. Serr M. Newman E.A. Hays T.S. The Drosophila tctex-1 light chain is dispensable for essential cytoplasmic dynein functions but is required during spermatid differentiation.Mol. Biol. Cell. 2004; 15: 3005-3014Crossref PubMed Scopus (47) Google Scholar). DYNLT1 is involved in cargo binding (11.Chuang J.Z. Yeh T.Y. Bollati F. Conde C. Canavosio F. Caceres A. Sung C.H. The dynein light chain Tctex-1 has a dynein-independent role in actin remodeling during neurite outgrowth.Dev. Cell. 2005; 9: 75-86Abstract Full Text Full Text PDF PubMed Scopus (87) Google Scholar), lymphocyte division (8.Campbell K.S. Cooper S. Dessing M. Yates S. Buder A. Interaction of p59fyn kinase with the dynein light chain, Tctex-1, and colocalization during cytokinesis.J. Immunol. 1998; 161: 1728-1737PubMed Google Scholar), vesicle transport (12.Mueller S. Cao X. Welker R. Wimmer E. Interaction of the poliovirus receptor CD155 with the dynein light chain Tctex-1 and its implication for poliovirus pathogenesis.J. Biol. Chem. 2002; 277: 7897-7904Abstract Full Text Full Text PDF PubMed Scopus (121) Google Scholar, 13.Nagano F. Orita S. Sasaki T. Naito A. Sakaguchi G. Maeda M. Watanabe T. Kominami E. Uchiyama Y. Takai Y. Interaction of Doc2 with tctex-1, a light chain of cytoplasmic dynein. Implication in dynein-dependent vesicle transport.J. Biol. Chem. 1998; 273: 30065-30068Abstract Full Text Full Text PDF PubMed Scopus (59) Google Scholar, 14.Ohka S. Matsuda N. Tohyama K. Oda T. Morikawa M. Kuge S. Nomoto A. Receptor (CD155)-dependent endocytosis of poliovirus and retrograde axonal transport of the endosome.J. Virol. 2004; 78: 7186-7198Crossref PubMed Scopus (101) Google Scholar), and human embryo implantation (15.Nadano D. Nakayama J. Matsuzawa S. Sato T.A. Matsuda T. Fukuda M.N. Human tastin, a proline-rich cytoplasmic protein, associates with the microtubular cytoskeleton.Biochem. J. 2002; 364: 669-677Crossref PubMed Scopus (36) Google Scholar). DYNLT1 is known to undergo phosphorylation during apical delivery of rhodopsin (16.Yeh T.Y. Peretti D. Chuang J.Z. Rodriguez-Boulan E. Sung C.H. Regulatory dissociation of Tctex-1 light chain from dynein complex is essential for the apical delivery of rhodopsin.Traffic. 2006; 7: 1495-1502Crossref PubMed Scopus (34) Google Scholar) and during its interaction with the bone morphogenetic receptor type II (BMPRII) (17.Machado R.D. N. C. R. interaction between and Tctex-1, a light chain of is and by mutations Mol. Genet. 2003; 12: PubMed Scopus Google Scholar). DYNLT1 function in dynein-independent as a cell by its interaction with neurite P. S. Chuang J.Z. Yeh T.Y. Conde C. Caceres A. Sung C.H. protein interaction with the dynein Tctex-1 neurite J. PubMed Scopus Google Scholar), axonal and of in (11.Chuang J.Z. Yeh T.Y. Bollati F. Conde C. Canavosio F. Caceres A. Sung C.H. The dynein light chain Tctex-1 has a dynein-independent role in actin remodeling during neurite outgrowth.Dev. Cell. 2005; 9: 75-86Abstract Full Text Full Text PDF PubMed Scopus (87) Google Scholar, J.Z. T.A. Sung C.H. of cytoplasmic expression of 14 kDa dynein light in PubMed Google Scholar). is to by DYNLT1 and its is the interaction of DYNLT1 with proteins D. D. J. M. M. R. of the factor PubMed Scopus Google Scholar). DYNLT1 is a for in adult brain C. Chuang J.Z. Sung C.H. light chain Tctex-1 in adult 2006; PubMed Google Scholar). DYNLT1 was identified which cells in and adult brain N. A. Chuang J.Z. Sung C.H. Identification of the Tctex-1 that expression to cells in and adult PubMed Scopus Google Scholar). The of DYNLT1 in A. M. R. and Tctex-1 the of from 12: PubMed Scopus (69) Google Scholar). The of the of DYNLT1 promoter to adult stem cells and the of sequence has been C.H. Chuang J.Z. Tctex-1 sequence as stem cell Google Google Scholar). DYNLT1 is to have in germ cells as DYNLT1 was to essential during spermatid in Drosophila (10.Li M.G. Serr M. Newman E.A. Hays T.S. The Drosophila tctex-1 light chain is dispensable for essential cytoplasmic dynein functions but is required during spermatid differentiation.Mol. Biol. Cell. 2004; 15: 3005-3014Crossref PubMed Scopus (47) Google Scholar) and a mouse DYNLT1 was identified in the dynein light chain of sperm M. Y. H. R. K. A dynein light chain of sperm is a of mouse which is by a gene of the t complex sterility 1998; PubMed Scopus Google Scholar, A. M. Chuang J.Z. C. K. T. Sung C.H. of Tctex-1 and of Cell Biol. PubMed Scopus Google Scholar). the expression of DYNLT1 in human germ cells and its with human male factor are study the association between and in infertile human males and the possible function of DYNLT1 in cell division and differentiation. membrane to DYNLT1 and PCR GC1-spg cell line and were were from study was by the and Human of for for the study were a from the have a in the and were as fertile males of infertile of male factor infertility were as infertile males in this These infertile males have and were The by of The were to for to with a and the were study of (n = 14), asthenozoospermic (n = 15), oligozoospermic (n = 20) and teratozoospermic (n = 23) The spermatozoa were by for The was in and was of as and was used for the other was used for protein sperm was in 1 of for with using a was by the of was to the for for and for The was a and using The was in and in of the total was for and to for using the The the and to the The was PCR for DYNLT1 and were using The of the used are in The chain was as 1 of was with and 1 of and in a for by of for for for and a for were to DYNLT1 from the in the PCR the of of was and other the The PCR were with of and the were by on a of using and The PCR were on a and on using the of DYNLT1 were and were to the levels of using of used for in a The DYNLT1 were using to in and were The of the gene the was by was using the The was in a PCR the were and were in The were by using were using the were using and a sequence was The of the was using the sperm was in of the 1 1 and 1 and by three of was for The was as protein and The protein were with of and were for were by for were on a The proteins were to the membrane of for using a cell The was and the were in and in of in for the were three with The were with DYNLT1 a of in for and were three with was a of in for The were with three The were by the in and in the was The were on using the of DYNLT1 and were and were to the levels of using of the sperm was using for and in for These were for in and to the binding of cellular proteins to the The were in three changes of and were with a in for The were three in and with in for 1 in the The were with and in The cells were The mouse of DYNLT1 was from mouse total using gene and with and the Dynlt1 and the were with and and the were and E. The were screened by PCR using and The and of the in the was by using The from the was for The cell line were in Dulbecco's Eagles with and in a and The cells were and in and in with and and to The was with 1 to and the was with of expression using and for the was with and and for in The cells with were and and the total protein was using GC1-spg cells with as The and cytoplasmic and the and both these were as protein The of the protein was by and the of the were using to a of 1 of proteins from was to to the of the The were for and the was The was to for with The were using a and were with of from the were on a The was using that and to and of protein for protein as well as for the protein included for were as for high and by The protein were by the mouse from the protein was to The for protein was in a that a was required to have a protein was required to have three and a protein was required to have 1 for was to for and for of was as and was as a was as the used with a of 1 identified with with a of or were as were using the function of and was by the of identified between the a higher than of either or was to of significantly levels of The of proteins were using to the proteins on of proteins in DYNLT1 GC1-spg cells were using A was the to the and the of with the of from and Western blot on of (n = 14), (n = 15), (n = 20) and (n = 23) were to t using were between and of the and a was as The of of the was and as a Western protein from the spermatozoa of fertile males showed a 14 kDa that was by DYNLT1 and was in the protein of spermatozoa from infertile and of the infertile showed levels of expression of DYNLT1 and was used as The of DYNLT1 were to the levels using the The expression levels of DYNLT1 in infertile were significantly lower when compared with that of fertile The localization of DYNLT1 on spermatozoa was using The spermatozoa from fertile males showed DYNLT1 localization on the head, and tail The spermatozoa from infertile males showed a complete absence of DYNLT1 from the tail this protein was present on the and of these cells in asthenozoospermic oligozoospermic and teratozoospermic PCR using DYNLT1 from the from the germ cells from of a and was and its was by The sequence was in the A of this gene a protein with amino Human males to have spermatogenic showed absence and or levels and of expression of DYNLT1 in the germ cells as from analysis. a infertile showed levels of DYNLT1 expression as the The expression levels of DYNLT1 in infertile which were significantly lower than of fertile individuals were expressed as using the was in the from germ cells of fertile and infertile individuals absence of lymphocyte in the germ cells from the from the from from human is as of the E. with were screened by PCR The were and the of the was by the sequence to GC1-spg cells with and the were for to the over expression of DYNLT1 and The cells were and for protein and The of and the for protein for and protein are in and The showed expressed proteins and was and were the expressed proteins were identified by and the proteins with gene were with expression level changes The predicted proteins which were identified by were with expression level changes The was used to the and proteins with to DYNLT1 over expressed proteins were 17 to protein The of the proteins were by acid binding proteins and cytoskeletal proteins the proteins were three The was used to the the expressed proteins and showed of protein protein cytoskeletal proteins and proteins were no in of the proteins of and proteins in GC1-spg cells DYNLT1, using DYNLT1 gene family was identified as a member of the t-complex of the mouse, which has been linked with male germ cell development and function in mouse (1.Lader E. Ha H.S. O'Neill M. Artzt K. Bennett D. tctex-1: a candidate gene family for a mouse t complex sterility locus.Cell. 1989; 58: 969-979Abstract Full Text PDF PubMed Google Scholar, A. Y. of male and meiotic loci in the mouse t complex using chromosome Google Scholar) and the C. R. G. P. R. the Drosophila of a murine t-complex a dynein light chain, is required for of Genet. PubMed Scopus Google Scholar, M.G. Serr M. Newman E.A. Hays T.S. The Drosophila tctex-1 light chain is dispensable for essential cytoplasmic dynein functions but is required during spermatid differentiation.Mol. Biol. Cell. 2004; 15: 3005-3014Crossref PubMed Scopus Google Scholar). Though defects in DYNLT1 expression were linked to in both mouse and there has been no the association between the expression of this gene and in human males. to the role of DYNLT1 by mice for a wild-type bacterial artificial chromosome from the genes and which are in t t mice that of was to in mice A. in or cause proximal t male mouse sterility but ratio 2005; PubMed Scopus Google Scholar). the of the in this study and was the of both with the the of the study in DYNLT1 as a The presented in this for the that human males with spermatogenic present expression of germ The of of the in this study are in sperm of the used in this indicated are of the observations in a DYNLT1 was expressed in infertile individuals compared with fertile individuals the and and and the expression of protein to spermatogenic A. S.M. K. expression of binding is associated with spermatogenic in Scholar). The of DYNLT1 from germ cells present in the was by the expression of in these individuals The localization of DYNLT1 in the tail segments of spermatozoa from fertile human males and its absence in the spermatozoa from infertile a role for this in flagellar DYNLT1 was identified as a of the microtubular (5.Harrison A. Olds-Clarke P. King S.M. Identification of the t complex-encoded cytoplasmic dynein light chain tctex1 in inner arm I1 supports the involvement of flagellar dyneins in meiotic drive.J. Cell Biol. 1998; 140: 1137-1147Crossref PubMed Scopus (118) Google Scholar) of the cells and was in functions cytoskeletal and cellular P. S. Chuang J.Z. Yeh T.Y. Conde C. Caceres A. Sung C.H. protein interaction with the dynein Tctex-1 neurite J. PubMed Scopus (59) Google Scholar, J.Z. Yeh T.Y. Bollati F. Conde C. Canavosio F. Caceres A. Sung C.H. The dynein light chain Tctex-1 has a dynein-independent role in actin remodeling during neurite outgrowth.Dev. Cell. 2005; 9: 75-86Abstract Full Text Full Text PDF PubMed Scopus Google Scholar). t-complex protein was localized in mouse sperm tails K. Artzt K. a sperm tail protein to the Biol. 1995; PubMed Scopus Google Scholar) and of sperm K. K. arm dynein light chain is of sperm PubMed Scopus Google Scholar). The genes in t-complex of the mouse have role in male germ cell development and The t-complex has several genes essential for tail and T. F. S. M. E. Y. Y. and of a human homologue of murine to Cell Genet. 1996; PubMed Scopus Google Scholar). Dynlt1 is of the t complex genes and its and germ cell expression as a candidate gene for male sterility E. Ha H.S. O'Neill M. Artzt K. Bennett D. tctex-1: a candidate gene family for a mouse t complex sterility locus.Cell. 1989; 58: 969-979Abstract Full Text PDF PubMed Scopus Google Scholar). The of DYNLT1 in mouse sperm and its involvement in meiotic were A. Olds-Clarke P. King S.M. Identification of the t complex-encoded cytoplasmic dynein light chain tctex1 in inner arm I1 supports the involvement of flagellar dyneins in meiotic drive.J. Cell Biol. 1998; 140: 1137-1147Crossref PubMed Scopus Google Scholar). is DYNLT1 expression is to cell C. Chuang J.Z. Sung C.H. light chain Tctex-1 in adult 2006; Scopus Google Scholar) and in N. A. Chuang J.Z. Sung C.H. Identification of the Tctex-1 that expression to cells in and adult PubMed Scopus Google Scholar) in the adult stem expression in the adult the of role in in the cells are the to and as well as have to cells M. S. Y. transcriptional of and adult stem 2002; PubMed Scopus Google Scholar). The expression of X. J. T. Y. S. J. G. J. the in mouse stem PubMed Scopus Google Scholar), and J. stem cell PubMed Scopus Google Scholar) were for the of or in both embryo and adult tissues S.M. of stem cell and a of the and with complexes and stem cell PubMed Scopus Google Scholar). the of proteins which showed changes in levels of expression as a of Dynlt1 in cells protein associated with is a complex during which the of stem cell to spermatozoa the and differentiation. The and and of R. Identification of a protein and candidate expressed in Cell Biol. 9: PubMed Scopus Google Scholar). In the present study, of the proteins by were molecular cytoskeletal and acid binding proteins which are involved in cell cycle regulation. In our we the up-regulation of and of chaperones proteins and protein subunits in The expression of family of chaperones in of mouse spermatogenic cells of proteins by mouse spermatogenic Cell. Biol. PubMed Scopus Google Scholar) and the expression of during and its localized over the were K. K.S. J. C. K. M.F. M. The t complex 1 is associated with the cytoplasmic of Golgi 1989; Full Text PDF PubMed Scopus Google Scholar). the of proteins in sperm and spermatogenic R.J. The role of molecular chaperones in and the of PubMed Scopus Google Scholar). the molecular chaperones identified in the present study have role in and sperm The changes in the male germ cell were as in spermatogenic The of the male germ Cell. PubMed Scopus Google Scholar). The proteins were of cytoskeletal which are involved in cell cycle regulation, and that Dynlt1 have in the of germ cell during spermatogenesis. The proteins were acid binding proteins and proteins and transcriptional and The up-regulation of cytoskeletal proteins and acid binding proteins with to DYNLT1 over expression that Dynlt1 have role in of germ cells by during in the The showed of proteins the which included proteins cytoskeletal proteins molecular chaperones and proteins of the proteins in our cytoplasmic 1 actin protein and the molecular chaperones protein and were to expressed in mouse stem cells S. G. A. N. L. P. of mouse stem PubMed Scopus Google Scholar). These that Dynlt1 have role in to Chuang that Dynlt1 the actin a during neurite J.Z. Yeh T.Y. Bollati F. Conde C. Canavosio F. Caceres A. Sung C.H. The dynein light chain Tctex-1 has a dynein-independent role in actin remodeling during neurite outgrowth.Dev. Cell. 2005; 9: 75-86Abstract Full Text Full Text PDF PubMed Scopus Google Scholar). the up-regulation of cytoskeletal proteins associated with in cells in to the of over the DYNLT1 from a sterility gene a gene with of DYNLT1 has been used for the cells in a cell C.H. Chuang J.Z. Tctex-1 sequence as stem cell Google Google Scholar). DYNLT1 a role in of neurite and and these effects are from its cargo role for dynein motor transport (11.Chuang J.Z. Yeh T.Y. Bollati F. Conde C. Canavosio F. Caceres A. Sung C.H. The dynein light chain Tctex-1 has a dynein-independent role in actin remodeling during neurite outgrowth.Dev. Cell. 2005; 9: 75-86Abstract Full Text Full Text PDF PubMed Scopus (87) Google Scholar). DYNLT1 has a role in cell cycle A. M. Chuang J.Z. C. K. T. Sung C.H. of Tctex-1 and of Cell Biol. PubMed Scopus Google Scholar). male infertility is of the expression of DYNLT1 in the stem cells is to In this study a in the expression of DYNLT1 in the germ cells of infertile human males and DYNLT1 in cell division and differentiation. with