TY - JOUR
T1 - Mouse survival motor neuron alleles that mimic SMN2 splicing and are inducible rescue embryonic lethality early in development but not late
AU - Hammond, Suzan M.
AU - Gogliotti, Rocky G.
AU - Rao, Vamshi
AU - Beauvais, Ariane
AU - Kothary, Rashmi
AU - DiDonato, Christine J.
PY - 2010
Y1 - 2010
N2 - Spinal muscular atrophy (SMA) is caused by low survival motor neuron (SMN) levels and patients represent a clinical spectrum due primarily to varying copies of the survival motor neuron-2 (SMN2) gene. Patient and animals studies show that disease severity is abrogated as SMN levels increase. Since therapies currently being pursued target the induction of SMN, it will be important to understand the dosage, timing and cellular requirements of SMN for disease etiology and potential therapeutic intervention. This requires new mouse models that can induce SMN temporally and/or spatially. Here we describe the generation of two hypomorphic Smn alleles, SmnC-T-Neo and Smn2B-Neo. These alleles mimic SMN2 exon 7 splicing, titre Smn levels and are inducible. They were specifically designed so that up to three independent lines of mice could be generated, herein we describe two. In a homozygous state each allele results in embryonic lethality. Analysis of these mutants indicates that greater than 5% of Smn protein is required for normal development. The severe hypomorphic nature of these alleles is caused by inclusion of a loxP-flanked neomycin gene selection cassette in Smn intron 7, which can be removed with Cre recombinase. In vitro and in vivo experiments demonstrate these as inducible Smn alleles. When combined with an inducible Cre mouse, embryonic lethality caused by low Smn levels can be rescued early in gestation but not late. This provides direct genetic evidence that a therapeutic window for SMN inductive therapies may exist. Importantly, these lines fill a void for inducible Smn alleles. They also provide a base from which to generate a large repertoire of SMA models of varying disease severities when combined with other Smn alleles or SMN2-containing mice.
AB - Spinal muscular atrophy (SMA) is caused by low survival motor neuron (SMN) levels and patients represent a clinical spectrum due primarily to varying copies of the survival motor neuron-2 (SMN2) gene. Patient and animals studies show that disease severity is abrogated as SMN levels increase. Since therapies currently being pursued target the induction of SMN, it will be important to understand the dosage, timing and cellular requirements of SMN for disease etiology and potential therapeutic intervention. This requires new mouse models that can induce SMN temporally and/or spatially. Here we describe the generation of two hypomorphic Smn alleles, SmnC-T-Neo and Smn2B-Neo. These alleles mimic SMN2 exon 7 splicing, titre Smn levels and are inducible. They were specifically designed so that up to three independent lines of mice could be generated, herein we describe two. In a homozygous state each allele results in embryonic lethality. Analysis of these mutants indicates that greater than 5% of Smn protein is required for normal development. The severe hypomorphic nature of these alleles is caused by inclusion of a loxP-flanked neomycin gene selection cassette in Smn intron 7, which can be removed with Cre recombinase. In vitro and in vivo experiments demonstrate these as inducible Smn alleles. When combined with an inducible Cre mouse, embryonic lethality caused by low Smn levels can be rescued early in gestation but not late. This provides direct genetic evidence that a therapeutic window for SMN inductive therapies may exist. Importantly, these lines fill a void for inducible Smn alleles. They also provide a base from which to generate a large repertoire of SMA models of varying disease severities when combined with other Smn alleles or SMN2-containing mice.
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U2 - 10.1371/journal.pone.0015887
DO - 10.1371/journal.pone.0015887
M3 - Article
C2 - 21249120
AN - SCOPUS:78650827775
SN - 1932-6203
VL - 5
JO - PloS one
JF - PloS one
IS - 12
M1 - e15887
ER -