title: Uncoupling skeletal and connective tissue patterning: conditional deletion in cartilage progenitors reveals cell-autonomous requirements for Lmx1b in dorsal-ventral limb patterning.
abstract: Integration of muscle, connective tissue and skeletal patterning during development is essential for proper functioning of the musculoskeletal system. How this integration is achieved is poorly understood. There is ample evidence suggesting that skeletal pattern is programmed autonomously, whereas muscle pattern is, for the most part, programmed non-cell-autonomously. Connective tissues depend upon both muscle and skeletal tissues for their proper survival and development. Here, we employed a novel approach to dissect the coordination of musculoskeletal patterning during mouse limb development. Using both conditional gain- and loss-of-function approaches, we selectively deleted or activated the LIM-homeodomain transcription factor Lmx1b in skeletal progenitors using a Sox9-Cre knock-in allele. As Lmx1b is both necessary and sufficient to specify dorsal pattern, this approach allowed us to investigate the effect of selectively deleting or activating Lmx1b in skeletal progenitors on muscle, connective and skeletal tissues during limb development. Our results indicate that whereas Lmx1b activity is required autonomously in skeletal progenitors to direct dorsal pattern, loss or gain of Lmx1b activity in skeletal progenitors has no effect on muscle or connective tissue patterning. Hence, we show for the first time that skeletal and connective tissue patterning can be uncoupled, indicating a degree of autonomy in the formation of the musculoskeletal system.
authors.affiliation: Program in Genes and Development, University of Texas Health Sciences Center, Houston Graduate School of Biomedical Sciences, Houston, TX 77030, USA.
authors.forename: Ying
authors.initials: Y
authors.lastname: Li
authors.forename: Qiong
authors.initials: Q
authors.lastname: Qiu
authors.forename: Spenser S
authors.initials: SS
authors.lastname: Watson
authors.forename: Ronen
authors.initials: R
authors.lastname: Schweitzer
authors.forename: Randy L
authors.initials: RL
authors.lastname: Johnson
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D019521:Body Patterning / Q000502:physiology*; D001842:Bone and Bones / Q000166:cytology / Q000502:physiology; D002356:Cartilage / Q000166:cytology*; D019070:Cell Lineage; D003238:Connective Tissue / Q000033:anatomy & histology / Q000502:physiology; D005121:Extremities / Q000033:anatomy & histology / Q000196:embryology; D055879:Gene Knock-In Techniques; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D007596:Joints / Q000033:anatomy & histology / Q000196:embryology / Q000378:metabolism; D060850:LIM-Homeodomain Proteins; D008648:Mesoderm / Q000166:cytology; D051379:Mice; D008822:Mice, Transgenic; D018482:Muscle, Skeletal / Q000166:cytology / Q000502:physiology; D010641:Phenotype; D055758:SOX9 Transcription Factor / Q000235:genetics / Q000378:metabolism; D013234:Stem Cells / Q000166:cytology / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D018398:Homeodomain Proteins; C112149:LIM homeobox transcription factor 1 beta; D060850:LIM-Homeodomain Proteins; D055758:SOX9 Transcription Factor; C527933:Sox9 protein, mouse; D014157:Transcription Factors