Limits...
The dissection of meiotic chromosome movement in mice using an in vivo electroporation technique.

Shibuya H, Morimoto A, Watanabe Y - PLoS Genet. (2014)

Bottom Line: Further, during bouquet stage, telomeres are constrained near the MTOC, resulting in the transient suppression of telomere mobility and nuclear rotation.In contrast, actin regulates the oscillatory changes in nuclear shape.Our data provide the mechanical scheme for meiotic chromosome movement throughout prophase I in mammals.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Chromosome Dynamics, Institute of Molecular and Cellular Biosciences, University of Tokyo, Tokyo, Japan.

ABSTRACT
During meiosis, the rapid movement of telomeres along the nuclear envelope (NE) facilitates pairing/synapsis of homologous chromosomes. In mammals, the mechanical properties of chromosome movement and the cytoskeletal structures responsible for it remain poorly understood. Here, applying an in vivo electroporation (EP) technique in live mouse testis, we achieved the quick visualization of telomere, chromosome axis and microtubule organizing center (MTOC) movements. For the first time, we defined prophase sub-stages of live spermatocytes morphologically according to GFP-TRF1 and GFP-SCP3 signals. We show that rapid telomere movement and subsequent nuclear rotation persist from leptotene/zygotene to pachytene, and then decline in diplotene stage concomitant with the liberation of SUN1 from telomeres. Further, during bouquet stage, telomeres are constrained near the MTOC, resulting in the transient suppression of telomere mobility and nuclear rotation. MTs are responsible for these movements by forming cable-like structures on the NE, and, probably, by facilitating the rail-tacking movements of telomeres on the MT cables. In contrast, actin regulates the oscillatory changes in nuclear shape. Our data provide the mechanical scheme for meiotic chromosome movement throughout prophase I in mammals.

Show MeSH

Related in: MedlinePlus

Complementation assay by in vivo EPs.A, Equator images of Sun1−/− spermatocytes expressing GFP-SUN1 or SUN1-MYC stained for telomere TRF1 (green), GFP or MYC (blue) and SCP3 (red). The graph shows the number of internal telomeres (TRF1 foci) in wild type (zygotene to pachytene), Sun1−/− and Sun1−/− expressing exogenous SUN1 protein. B, Quantification of TRF1 foci number in wild type, Sun1−/− spermatocytes and Sun1−/− spermatocytes expressing exogenous SUN1 protein. C, Representative pictures of Sun1−/− spermatocytes or Sun1−/− spermatocytes expressing SUN1-MYC stained for SCP3 (red), SCP1 (green) and MYC (blue). The median numbers are shown in the graphs. Bars, 5 µm.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4263375&req=5

pgen-1004821-g002: Complementation assay by in vivo EPs.A, Equator images of Sun1−/− spermatocytes expressing GFP-SUN1 or SUN1-MYC stained for telomere TRF1 (green), GFP or MYC (blue) and SCP3 (red). The graph shows the number of internal telomeres (TRF1 foci) in wild type (zygotene to pachytene), Sun1−/− and Sun1−/− expressing exogenous SUN1 protein. B, Quantification of TRF1 foci number in wild type, Sun1−/− spermatocytes and Sun1−/− spermatocytes expressing exogenous SUN1 protein. C, Representative pictures of Sun1−/− spermatocytes or Sun1−/− spermatocytes expressing SUN1-MYC stained for SCP3 (red), SCP1 (green) and MYC (blue). The median numbers are shown in the graphs. Bars, 5 µm.

Mentions: We next examined the functionality of the transgenes in testis. The inner nuclear membrane protein SUN1 is required for the nuclear peripheral distribution of meiotic telomeres, and the disruption of Sun1 prevents homologous pairing/synapsis due to the loss of meiotic chromosome movements [17], [19]. We confirmed that telomeres, represented by TRF1 foci, were partly detached from the NE in spermatocytes from Sun1−/− mice (15 internal telomeres/cell) (Fig. 2A). Strikingly, the exogenous expression of SUN1-MYC protein by in vivo EP largely restored the telomere attachment defects in Sun1−/− testes (1–2 internal telomeres/cell) (Fig. 2A).


The dissection of meiotic chromosome movement in mice using an in vivo electroporation technique.

Shibuya H, Morimoto A, Watanabe Y - PLoS Genet. (2014)

Complementation assay by in vivo EPs.A, Equator images of Sun1−/− spermatocytes expressing GFP-SUN1 or SUN1-MYC stained for telomere TRF1 (green), GFP or MYC (blue) and SCP3 (red). The graph shows the number of internal telomeres (TRF1 foci) in wild type (zygotene to pachytene), Sun1−/− and Sun1−/− expressing exogenous SUN1 protein. B, Quantification of TRF1 foci number in wild type, Sun1−/− spermatocytes and Sun1−/− spermatocytes expressing exogenous SUN1 protein. C, Representative pictures of Sun1−/− spermatocytes or Sun1−/− spermatocytes expressing SUN1-MYC stained for SCP3 (red), SCP1 (green) and MYC (blue). The median numbers are shown in the graphs. Bars, 5 µm.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4263375&req=5

pgen-1004821-g002: Complementation assay by in vivo EPs.A, Equator images of Sun1−/− spermatocytes expressing GFP-SUN1 or SUN1-MYC stained for telomere TRF1 (green), GFP or MYC (blue) and SCP3 (red). The graph shows the number of internal telomeres (TRF1 foci) in wild type (zygotene to pachytene), Sun1−/− and Sun1−/− expressing exogenous SUN1 protein. B, Quantification of TRF1 foci number in wild type, Sun1−/− spermatocytes and Sun1−/− spermatocytes expressing exogenous SUN1 protein. C, Representative pictures of Sun1−/− spermatocytes or Sun1−/− spermatocytes expressing SUN1-MYC stained for SCP3 (red), SCP1 (green) and MYC (blue). The median numbers are shown in the graphs. Bars, 5 µm.
Mentions: We next examined the functionality of the transgenes in testis. The inner nuclear membrane protein SUN1 is required for the nuclear peripheral distribution of meiotic telomeres, and the disruption of Sun1 prevents homologous pairing/synapsis due to the loss of meiotic chromosome movements [17], [19]. We confirmed that telomeres, represented by TRF1 foci, were partly detached from the NE in spermatocytes from Sun1−/− mice (15 internal telomeres/cell) (Fig. 2A). Strikingly, the exogenous expression of SUN1-MYC protein by in vivo EP largely restored the telomere attachment defects in Sun1−/− testes (1–2 internal telomeres/cell) (Fig. 2A).

Bottom Line: Further, during bouquet stage, telomeres are constrained near the MTOC, resulting in the transient suppression of telomere mobility and nuclear rotation.In contrast, actin regulates the oscillatory changes in nuclear shape.Our data provide the mechanical scheme for meiotic chromosome movement throughout prophase I in mammals.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Chromosome Dynamics, Institute of Molecular and Cellular Biosciences, University of Tokyo, Tokyo, Japan.

ABSTRACT
During meiosis, the rapid movement of telomeres along the nuclear envelope (NE) facilitates pairing/synapsis of homologous chromosomes. In mammals, the mechanical properties of chromosome movement and the cytoskeletal structures responsible for it remain poorly understood. Here, applying an in vivo electroporation (EP) technique in live mouse testis, we achieved the quick visualization of telomere, chromosome axis and microtubule organizing center (MTOC) movements. For the first time, we defined prophase sub-stages of live spermatocytes morphologically according to GFP-TRF1 and GFP-SCP3 signals. We show that rapid telomere movement and subsequent nuclear rotation persist from leptotene/zygotene to pachytene, and then decline in diplotene stage concomitant with the liberation of SUN1 from telomeres. Further, during bouquet stage, telomeres are constrained near the MTOC, resulting in the transient suppression of telomere mobility and nuclear rotation. MTs are responsible for these movements by forming cable-like structures on the NE, and, probably, by facilitating the rail-tacking movements of telomeres on the MT cables. In contrast, actin regulates the oscillatory changes in nuclear shape. Our data provide the mechanical scheme for meiotic chromosome movement throughout prophase I in mammals.

Show MeSH
Related in: MedlinePlus