title: Calretinin-positive L5a pyramidal neurons in the development of the paralemniscal pathway in the barrel cortex.
abstract: BACKGROUND
  The rodent barrel cortex has been established as an ideal model for studying the development and plasticity of a neuronal circuit. The barrel cortex consists of barrel and septa columns, which receive various input signals through distinct pathways. The lemniscal pathway transmits whisker-specific signals to homologous barrel columns, and the paralemniscal pathway transmits multi-whisker signals to both barrel and septa columns. The integration of information from both lemniscal and paralemniscal pathways in the barrel cortex is critical for precise object recognition. As the main target of the posterior medial nucleus (POm) in the paralemniscal pathway, layer 5a (L5a) pyramidal neurons are involved in both barrel and septa circuits and are considered an important site of information integration. However, information on L5a neurons is very limited. This study aims to explore the cellular features of L5a neurons and to provide a morphological basis for studying their roles in the development of the paralemniscal pathway and in information integration.
  
  
  RESULTS
  1. We found that the calcium-binding protein calretinin (CR) is dynamically expressed in L5a excitatory pyramidal neurons of the barrel cortex, and L5a neurons form a unique serrated pattern similar to the distributions of their presynaptic POm axon terminals. 2. Infraorbital nerve transection disrupts this unique alignment, indicating that it is input dependent. 3. The formation of the L5a neuronal alignment develops synchronously with barrels, which suggests that the lemniscal and paralemniscal pathways may interact with each other to regulate pattern formation and refinement in the barrel cortex. 4. CR is specifically expressed in the paralemniscal pathway, and CR deletion disrupts the unique L5a neuronal pattern, which indicates that CR may be required for the development of the paralemniscal pathway.
  
  
  CONCLUSIONS
  Our results demonstrate that L5a neurons form a unique, input-dependent serrated alignment during the development of cortical barrels and that CR may play an important role in the development of the paralemniscal pathway. Our data provide a morphological basis for studying the role of L5a pyramidal neurons in information integration within the lemniscal and paralemniscal pathways.
authors.affiliation: Key Laboratory of Developmental Genes and Human Diseases, MOE, Department of Anatomy and Neuroscience, Medical School, Southeast University, Nanjing, 210009, PR China. liujunhua1975@hotmail.com.
authors.forename: Junhua
authors.initials: J
authors.lastname: Liu
authors.affiliation: Key Laboratory of Developmental Genes and Human Diseases, MOE, Department of Anatomy and Neuroscience, Medical School, Southeast University, Nanjing, 210009, PR China. myqj2006@126.com.
authors.forename: Bin
authors.initials: B
authors.lastname: Liu
authors.affiliation: Key Laboratory of Developmental Genes and Human Diseases, MOE, Department of Anatomy and Neuroscience, Medical School, Southeast University, Nanjing, 210009, PR China. jiaoxiake08@163.com.
authors.forename: XiaoYun
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Developmental Genes and Human Diseases, MOE, Department of Anatomy and Neuroscience, Medical School, Southeast University, Nanjing, 210009, PR China. abcyu0517@gmail.com.
authors.forename: Baocong
authors.initials: B
authors.lastname: Yu
authors.affiliation: Institute of Neurobiology, Institutes of Brain Science and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai, 200032, PR China. guanwuqiang@gmail.com.
authors.forename: Wuqiang
authors.initials: W
authors.lastname: Guan
authors.affiliation: Key Laboratory of Developmental Genes and Human Diseases, MOE, Department of Anatomy and Neuroscience, Medical School, Southeast University, Nanjing, 210009, PR China. wangkunwj@163.com.
authors.forename: Kun
authors.initials: K
authors.lastname: Wang
authors.affiliation: Key Laboratory of Developmental Genes and Human Diseases, MOE, Department of Anatomy and Neuroscience, Medical School, Southeast University, Nanjing, 210009, PR China. ate5455@163.com.
authors.forename: Yang
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Key Laboratory of Developmental Genes and Human Diseases, MOE, Department of Anatomy and Neuroscience, Medical School, Southeast University, Nanjing, 210009, PR China. gongyifan1987@gmail.com.
authors.forename: Yifan
authors.initials: Y
authors.lastname: Gong
authors.affiliation: Key Laboratory of Developmental Genes and Human Diseases, MOE, Department of Anatomy and Neuroscience, Medical School, Southeast University, Nanjing, 210009, PR China. wuxiaojing0204@hotmail.com.
authors.forename: Xiaojing
authors.initials: X
authors.lastname: Wu
authors.affiliation: Department of Genetic and Behavioral Neuroscience, Gunma University Graduate School of Medicine, 3-39-22 Showa-machi, Maebashi, 371-8511, Japan. yochio@gunma-u.ac.jp.
authors.forename: Yuchio
authors.initials: Y
authors.lastname: Yanagawa
authors.affiliation: Department of Anatomy, Histology and Embryology, K.K. Leung Brain Research Centre, School of Basic Medicine, Fourth Military Medical University, Xi'an, 710032, PR China. devneuro@fmmu.edu.cn.
authors.forename: Shengxi
authors.initials: S
authors.lastname: Wu
authors.affiliation: Key Laboratory of Developmental Genes and Human Diseases, MOE, Department of Anatomy and Neuroscience, Medical School, Southeast University, Nanjing, 210009, PR China. zhaocj@seu.edu.cn.|Center of Depression, Beijing Institute for Brain Disorders, Beijing, 100069, PR China. zhaocj@seu.edu.cn.
authors.forename: Chunjie
authors.initials: C
authors.lastname: Zhao
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D064032:Calbindin 2 / Q000378:metabolism*; D005260:Female; D059330:GABAergic Neurons / Q000378:metabolism; D007395:Interneurons / Q000378:metabolism; D008297:Male; D018345:Mice, Knockout; D009154:Mutation; D009434:Neural Pathways / Q000378:metabolism*; D065821:Pontine Tegmentum / Q000378:metabolism*; D017966:Pyramidal Cells / Q000378:metabolism*; D013003:Somatosensory Cortex / Q000166:cytology* / Q000378:metabolism*; D014738:Vibrissae / Q000294:innervation*
chemical_list: D064032:Calbindin 2