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Open Access Research

Secretagogin is expressed in sensory CGRP neurons and in spinal cord of mouse and complements other calcium-binding proteins, with a note on rat and human

Tie-Jun Sten Shi123*, Qiong Xiang12, Ming-Dong Zhang23, Giuseppe Tortoriello49, Henrik Hammarberg5, Jan Mulder6, Kaj Fried3, Ludwig Wagner7, Anna Josephson2, Mathias Uhlén8, Tibor Harkany49 and Tomas Hökfelt2

  • * Corresponding author: Tie-Jun Sten Shi Teijun.Shi@ki.se

  • † Equal contributors

Author Affiliations

1 School of Life Science and Technology, Harbin Institute of Technology, 150001, Harbin, China

2 Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden

3 Department of Dental Medicine, Karolinska Institutet, Stockholm, Sweden

4 Division of Molecular Neurobiology, Department of Medical Biochemistry & Biophysics, Karolinska Institutet, Stockholm, Sweden

5 Department of Clinical Science and Education, Södersjukhuset (The Southern Hospital), Karolinska Institutet, Stockholm, Sweden

6 Department of Neuroscience, Science for Life Laboratory, Karolinska Institutet, Stockholm, Sweden

7 Department of Medicine III, Medical University of Vienna, Vienna, Austria

8 Science for Life Laboratory, Albanova University Center, Royal Institute of Technology (KTH), Stockholm, Sweden

9 European Neuroscience Institute, University of Aberdeen, Aberdeen, UK

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Molecular Pain 2012, 8:80  doi:10.1186/1744-8069-8-80

Published: 29 October 2012

Abstract

Background

Secretagogin (Scgn), a member of the EF-hand calcium-binding protein (CaBP) superfamily, has recently been found in subsets of developing and adult neurons. Here, we have analyzed the expression of Scgn in dorsal root ganglia (DRGs) and trigeminal ganglia (TGs), and in spinal cord of mouse at the mRNA and protein levels, and in comparison to the well-known CaBPs, calbindin D-28k, parvalbumin and calretinin. Rat DRGs, TGs and spinal cord, as well as human DRGs and spinal cord were used to reveal phylogenetic variations.

Results

We found Scgn mRNA expressed in mouse and human DRGs and in mouse ventral spinal cord. Our immunohistochemical data showed a complementary distribution of Scgn and the three CaBPs in mouse DRG neurons and spinal cord. Scgn was expressed in ~7% of all mouse DRG neuron profiles, mainly small ones and almost exclusively co-localized with calcitonin gene-related peptide (CGRP). This co-localization was also seen in human, but not in rat DRGs. Scgn could be detected in the mouse sciatic nerve and accumulated proximal to its constriction. In mouse spinal cord, Scgn-positive neuronal cell bodies and fibers were found in gray matter, especially in the dorsal horn, with particularly high concentrations of fibers in the superficial laminae, as well as in cell bodies in inner lamina II and in some other laminae. A dense Scgn-positive fiber network and some small cell bodies were also found in the superficial dorsal horn of humans. In the ventral horn, a small number of neurons were Scgn-positive in mouse but not rat, confirming mRNA distribution. Both in mouse and rat, a subset of TG neurons contained Scgn. Dorsal rhizotomy strongly reduced Scgn fiber staining in the dorsal horn. Peripheral axotomy did not clearly affect Scgn expression in DRGs, dorsal horn or ventral horn neurons in mouse.

Conclusions

Scgn is a CaBP expressed in a subpopulation of nociceptive DRG neurons and their processes in the dorsal horn of mouse, human and rat, the former two co-expressing CGRP, as well as in dorsal horn neurons in all three species. Functional implications of these findings include the cellular refinement of sensory information, in particular during the processing of pain.

Keywords:
Calbindin D-28k; Calretinin; Dorsal horn; Dorsal root ganglion; Nerve injury; Parvalbumin; Trigeminal ganglion