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Third-party-funded project

Co-regulation of survival of motor neurons (SMN) protein and ist interactor SIP1 during development and in spinal muscular atrophy

Project management at the University of Würzburg:

Participating scientists:

Spinal muscular atrophy (SMA) is a neuromuscular disease characterized by the degeneration of motor neurons in the spinal cord. The disease is caused by mutations of the survival of motor neuron 1 gene (SMN1), resulting in a reduced production of functional SMN protein. A major question unanswered thus far is why reduced amounts of ubiquitously expressed SMN protein specifically cause the degeneration of motor neurons without affecting other somatic cell types. In a first attempt to address this issue we have investigated the Smn interacting protein 1 (Sip1), with an emphasis on its developmental expression and subcellular distribution in spinal motor neurons in relation to Smn. By confocal immunofluorescence studies we provide evidence that a significant amount of Smn does not co-localize with Sip1 in neurites of motor neurons, indicating that Smn may exert motor neuron-specific functions that are not dependent on Sip1. Sip1 is highly expressed in the spinal cord during early development and expression decreases in parallel with Smn during postnatal development. Strikingly, reduced production of Smn as observed in cell lines derived from SMA patients or in a mouse model for SMA coincides with a simultaneous reduction of Sip1. The finding that expression of Sip1 and Smn is tightly co-regulated, together with the unique localization of Smn in neurites, may help in understanding the motor neuron-specific defects observed in SMA patients.

Key words:
    Spinal muscular atrophy
    Transgenic mice

Projekt period: from 01.1999 to 12.2001

Funding institution:
DFG ( SFB 581 TP B1 ) ,Granting date: 18.08.1998
Sonstige Stiftung ( Schilling-Stiftung )
Landeshaushalt Wissenschaftsministerium

Preceding project:
DFG To61/8-4


Institute for Clinical Neurobiology