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Spinster homolog 2 (spns2) deficiency causes early onset progressive hearing loss.

Chen J, Ingham N, Kelly J, Jadeja S, Goulding D, Pass J, Mahajan VB, Tsang SH, Nijnik A, Jackson IJ, White JK, Forge A, Jagger D, Steel KP - PLoS Genet. (2014)

Bottom Line: The mechanism of action of Spns2 is still elusive in mammals.Targeted inactivation of Spns2 in red blood cells, platelets, or lymphatic or vascular endothelial cells did not affect hearing, but targeted ablation of Spns2 in the cochlea using a Sox10-Cre allele produced a similar auditory phenotype to the original mutation, suggesting that local Spns2 expression is critical for hearing in mammals.These findings indicate that Spns2 is required for normal maintenance of the EP and hence for normal auditory function, and support a role for S1P signalling in hearing.

View Article: PubMed Central - PubMed

Affiliation: Wellcome Trust Sanger Institute, Hinxton, Cambridge, United Kingdom; Wolfson Centre for Age-Related Diseases, King's College London, London, United Kingdom.

ABSTRACT
Spinster homolog 2 (Spns2) acts as a Sphingosine-1-phosphate (S1P) transporter in zebrafish and mice, regulating heart development and lymphocyte trafficking respectively. S1P is a biologically active lysophospholipid with multiple roles in signalling. The mechanism of action of Spns2 is still elusive in mammals. Here, we report that Spns2-deficient mice rapidly lost auditory sensitivity and endocochlear potential (EP) from 2 to 3 weeks old. We found progressive degeneration of sensory hair cells in the organ of Corti, but the earliest defect was a decline in the EP, suggesting that dysfunction of the lateral wall was the primary lesion. In the lateral wall of adult mutants, we observed structural changes of marginal cell boundaries and of strial capillaries, and reduced expression of several key proteins involved in the generation of the EP (Kcnj10, Kcnq1, Gjb2 and Gjb6), but these changes were likely to be secondary. Permeability of the boundaries of the stria vascularis and of the strial capillaries appeared normal. We also found focal retinal degeneration and anomalies of retinal capillaries together with anterior eye defects in Spns2 mutant mice. Targeted inactivation of Spns2 in red blood cells, platelets, or lymphatic or vascular endothelial cells did not affect hearing, but targeted ablation of Spns2 in the cochlea using a Sox10-Cre allele produced a similar auditory phenotype to the original mutation, suggesting that local Spns2 expression is critical for hearing in mammals. These findings indicate that Spns2 is required for normal maintenance of the EP and hence for normal auditory function, and support a role for S1P signalling in hearing.

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Spns2 is expressed in the cochlea.A, Quantitative real time PCR showed that Spns2 is expressed in the cochlea (OC: organ of Corti, LW: lateral wall) and other organs including the eye, and a small amount of residual transcript remained in the homozygotes (red), ranging from 8% to 22% of wildtype (green) levels. Blue represents heterozygotes. B, X-gal staining showed expression of Spns2 in the cochlea in a homozygote at P10. Labelling (blue) was detected in the spiral prominence area (B,C), hair cells (B,D), Reissner's membrane, blood vessels in lateral wall (B,E), modiolar vessels (F), and bony shell (B). Labelling was also seen in the central projection of the auditory nerve (not shown). Nuclei are labelled in red. Scale bar: 50 µm in C, 20 µm in D,E,F,G.
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pgen-1004688-g002: Spns2 is expressed in the cochlea.A, Quantitative real time PCR showed that Spns2 is expressed in the cochlea (OC: organ of Corti, LW: lateral wall) and other organs including the eye, and a small amount of residual transcript remained in the homozygotes (red), ranging from 8% to 22% of wildtype (green) levels. Blue represents heterozygotes. B, X-gal staining showed expression of Spns2 in the cochlea in a homozygote at P10. Labelling (blue) was detected in the spiral prominence area (B,C), hair cells (B,D), Reissner's membrane, blood vessels in lateral wall (B,E), modiolar vessels (F), and bony shell (B). Labelling was also seen in the central projection of the auditory nerve (not shown). Nuclei are labelled in red. Scale bar: 50 µm in C, 20 µm in D,E,F,G.

Mentions: The introduction of a cassette with an additional splice acceptor site is predicted to interrupt normal transcription of the Spns2 gene (Fig. 1A) and generate a truncated non-functional transcript encoding the first 146 out of 549 amino acids of the Spns2 protein [4]. The Spns2tm1a/tm1a mice were fertile and can survive to adulthood, but were born at sub-Mendelian ratios (15.9% homozygotes among 747 offspring of heterozygous intercrosses; χ2 test, p<0.001). Quantitative real-time PCR revealed that residual transcript of Spns2 in cochleae, eyes and livers of the homozygous mice was substantially reduced compared to that of the heterozygous and wildtype mice (Fig. 2A). In order to completely inactivate expression of the Spns2 gene, we produced Spns2tm1b/tm1b mice by crossing Spns2tm1a/tm1a with mice ubiquitously expressing Cre recombinase to delete exon 3 in the germline. Spns2tm1b/tm1b mice were also fertile and can survive to adulthood with a birth rate at sub-Mendelian ratios (16.9% homozygotes among 266 offspring of heterozygous intercrosses; χ2 test, p = 0.0044). In other aspects of their phenotype, Spns2tm1b/tm1b mice were broadly similar to Spns2tm1a/tm1a mice (see http://www.sanger.ac.uk/mouseportal/search?query=spns2 for a comparison of the two lines). Spns2tm1a/tm1a mice were the first to be available and were used for most experiments in this study, and may be more relevant to human disease because most disease-causing mutations reduce rather than eliminate gene activity.


Spinster homolog 2 (spns2) deficiency causes early onset progressive hearing loss.

Chen J, Ingham N, Kelly J, Jadeja S, Goulding D, Pass J, Mahajan VB, Tsang SH, Nijnik A, Jackson IJ, White JK, Forge A, Jagger D, Steel KP - PLoS Genet. (2014)

Spns2 is expressed in the cochlea.A, Quantitative real time PCR showed that Spns2 is expressed in the cochlea (OC: organ of Corti, LW: lateral wall) and other organs including the eye, and a small amount of residual transcript remained in the homozygotes (red), ranging from 8% to 22% of wildtype (green) levels. Blue represents heterozygotes. B, X-gal staining showed expression of Spns2 in the cochlea in a homozygote at P10. Labelling (blue) was detected in the spiral prominence area (B,C), hair cells (B,D), Reissner's membrane, blood vessels in lateral wall (B,E), modiolar vessels (F), and bony shell (B). Labelling was also seen in the central projection of the auditory nerve (not shown). Nuclei are labelled in red. Scale bar: 50 µm in C, 20 µm in D,E,F,G.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4214598&req=5

pgen-1004688-g002: Spns2 is expressed in the cochlea.A, Quantitative real time PCR showed that Spns2 is expressed in the cochlea (OC: organ of Corti, LW: lateral wall) and other organs including the eye, and a small amount of residual transcript remained in the homozygotes (red), ranging from 8% to 22% of wildtype (green) levels. Blue represents heterozygotes. B, X-gal staining showed expression of Spns2 in the cochlea in a homozygote at P10. Labelling (blue) was detected in the spiral prominence area (B,C), hair cells (B,D), Reissner's membrane, blood vessels in lateral wall (B,E), modiolar vessels (F), and bony shell (B). Labelling was also seen in the central projection of the auditory nerve (not shown). Nuclei are labelled in red. Scale bar: 50 µm in C, 20 µm in D,E,F,G.
Mentions: The introduction of a cassette with an additional splice acceptor site is predicted to interrupt normal transcription of the Spns2 gene (Fig. 1A) and generate a truncated non-functional transcript encoding the first 146 out of 549 amino acids of the Spns2 protein [4]. The Spns2tm1a/tm1a mice were fertile and can survive to adulthood, but were born at sub-Mendelian ratios (15.9% homozygotes among 747 offspring of heterozygous intercrosses; χ2 test, p<0.001). Quantitative real-time PCR revealed that residual transcript of Spns2 in cochleae, eyes and livers of the homozygous mice was substantially reduced compared to that of the heterozygous and wildtype mice (Fig. 2A). In order to completely inactivate expression of the Spns2 gene, we produced Spns2tm1b/tm1b mice by crossing Spns2tm1a/tm1a with mice ubiquitously expressing Cre recombinase to delete exon 3 in the germline. Spns2tm1b/tm1b mice were also fertile and can survive to adulthood with a birth rate at sub-Mendelian ratios (16.9% homozygotes among 266 offspring of heterozygous intercrosses; χ2 test, p = 0.0044). In other aspects of their phenotype, Spns2tm1b/tm1b mice were broadly similar to Spns2tm1a/tm1a mice (see http://www.sanger.ac.uk/mouseportal/search?query=spns2 for a comparison of the two lines). Spns2tm1a/tm1a mice were the first to be available and were used for most experiments in this study, and may be more relevant to human disease because most disease-causing mutations reduce rather than eliminate gene activity.

Bottom Line: The mechanism of action of Spns2 is still elusive in mammals.Targeted inactivation of Spns2 in red blood cells, platelets, or lymphatic or vascular endothelial cells did not affect hearing, but targeted ablation of Spns2 in the cochlea using a Sox10-Cre allele produced a similar auditory phenotype to the original mutation, suggesting that local Spns2 expression is critical for hearing in mammals.These findings indicate that Spns2 is required for normal maintenance of the EP and hence for normal auditory function, and support a role for S1P signalling in hearing.

View Article: PubMed Central - PubMed

Affiliation: Wellcome Trust Sanger Institute, Hinxton, Cambridge, United Kingdom; Wolfson Centre for Age-Related Diseases, King's College London, London, United Kingdom.

ABSTRACT
Spinster homolog 2 (Spns2) acts as a Sphingosine-1-phosphate (S1P) transporter in zebrafish and mice, regulating heart development and lymphocyte trafficking respectively. S1P is a biologically active lysophospholipid with multiple roles in signalling. The mechanism of action of Spns2 is still elusive in mammals. Here, we report that Spns2-deficient mice rapidly lost auditory sensitivity and endocochlear potential (EP) from 2 to 3 weeks old. We found progressive degeneration of sensory hair cells in the organ of Corti, but the earliest defect was a decline in the EP, suggesting that dysfunction of the lateral wall was the primary lesion. In the lateral wall of adult mutants, we observed structural changes of marginal cell boundaries and of strial capillaries, and reduced expression of several key proteins involved in the generation of the EP (Kcnj10, Kcnq1, Gjb2 and Gjb6), but these changes were likely to be secondary. Permeability of the boundaries of the stria vascularis and of the strial capillaries appeared normal. We also found focal retinal degeneration and anomalies of retinal capillaries together with anterior eye defects in Spns2 mutant mice. Targeted inactivation of Spns2 in red blood cells, platelets, or lymphatic or vascular endothelial cells did not affect hearing, but targeted ablation of Spns2 in the cochlea using a Sox10-Cre allele produced a similar auditory phenotype to the original mutation, suggesting that local Spns2 expression is critical for hearing in mammals. These findings indicate that Spns2 is required for normal maintenance of the EP and hence for normal auditory function, and support a role for S1P signalling in hearing.

Show MeSH
Related in: MedlinePlus