Journal Article

Characterization of Ighmbp2 in motor neurons and implications for the pathomechanism in a mouse model of human spinal muscular atrophy with respiratory distress type 1 (SMARD1)

Katja Grohmann, Wilfried Rossoll, Igor Kobsar, Bettina Holtmann, Sibylle Jablonka, Carsten Wessig, Gisela Stoltenburg-Didinger, Utz Fischer, Christoph Hübner, Rudolf Martini and Michael Sendtner

in Human Molecular Genetics

Volume 13, issue 18, pages 2031-2042
Published in print September 2004 | ISSN: 0964-6906
Published online July 2004 | e-ISSN: 1460-2083 | DOI: http://dx.doi.org/10.1093/hmg/ddh222
Characterization of Ighmbp2 in motor neurons and implications for the pathomechanism in a mouse model of human spinal muscular atrophy with respiratory distress type 1 (SMARD1)

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Spinal muscular atrophy with respiratory distress type 1 (SMARD1) is caused by recessive mutations of the IGHMBP2 gene. The role of IGHMBP2 (immunoglobulin µ-binding protein 2) in the pathomechanism of motor neuron disease is unknown. We have generated antibodies against Ighmbp2 and showed that low levels of Ighmbp2 immunoreactivity are present in the nucleus of spinal motor neurons and high levels in cell bodies, axons and growth cones. Ighmbp2 protein levels are strongly reduced in neuromuscular degeneration (nmd) mice, the mouse model of SMARD1. Mutant mice show severe motor neuron degeneration before first clinical symptoms become apparent. The loss of motor neuron cell bodies in lumbar spinal cord is followed by axonal degeneration in corresponding nerves such as the femoral quadriceps and sciatic nerve and loss of axon terminals at motor endplates. Motor neuron degeneration and clinical symptoms then slowly progress until the mice die at the age of 3–4 months. In addition, myopathic changes seem to contribute to muscle weakness and especially to respiratory failure, which is characteristic of the disorder in humans. Cultured motor neurons from embryonic nmd mice did not show any abnormality with respect to survival, axonal growth or growth cone size, thus differing from motor neurons derived from, e.g. Smn (survival motor neuron) deficient mice, the model of spinal muscular atrophy (SMA). Our data suggest that the pathomechanism in SMARD1 is clearly distinct from other motor neuron diseases such as classic SMA.

Journal Article.  8032 words.  Illustrated.

Subjects: Genetics and Genomics

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