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Dynamic interplay of spectrosome and centrosome organelles in asymmetric stem cell divisions.

Bang C, Cheng J - PLoS ONE (2015)

Bottom Line: Utilizing time-lapse live cell imaging, customized tracking, and image processing programs, we found that most acentrosomal GSCs have the spectrosomes reposition from the basal end (wild type) to the apical end close to hub-GSC interface (acentrosomal GSCs).For acentrosomal GSCs, their mitotic spindles were still highly oriented and divided asymmetrically with longer mitosis duration, resulting in asymmetric divisions.Moreover, when the spectrosome was knocked out, the centrosomes velocity decreased and centrosomes located closer to hub-GSC interface.

View Article: PubMed Central - PubMed

Affiliation: Department of Bioengineering, The University of Illinois at Chicago, Chicago, Illinois, United States of America.

ABSTRACT
Stem cells have remarkable self-renewal ability and differentiation potency, which are critical for tissue repair and tissue homeostasis. Recently it has been found, in many systems (e.g. gut, neurons, and hematopoietic stem cells), that the self-renewal and differentiation balance is maintained when the stem cells divide asymmetrically. Drosophila male germline stem cells (GSCs), one of the best characterized model systems with well-defined stem cell niches, were reported to divide asymmetrically, where centrosome plays an important role. Utilizing time-lapse live cell imaging, customized tracking, and image processing programs, we found that most acentrosomal GSCs have the spectrosomes reposition from the basal end (wild type) to the apical end close to hub-GSC interface (acentrosomal GSCs). In addition, these apically positioned spectrosomes were mostly stationary while the basally positioned spectrosomes were mobile. For acentrosomal GSCs, their mitotic spindles were still highly oriented and divided asymmetrically with longer mitosis duration, resulting in asymmetric divisions. Moreover, when the spectrosome was knocked out, the centrosomes velocity decreased and centrosomes located closer to hub-GSC interface. We propose that in male GSCs, the spectrosome recruited to the apical end plays a complimentary role in ensuring proper spindle orientation when centrosome function is compromised.

No MeSH data available.


Related in: MedlinePlus

Dynamic migration patterns of spectrosomes are quantified utilizing time-lapse live-imaging.(A) Spectrosome localization in DSas4-mut becomes predominantly apical compared to wild type. #: p<0.05. (B) Live image sequences shows apically (to the hub cells) migrating spectrosome in a dividing DSas4-mut GSC. Arrowhead: spectrosome. *: hub cells. Yellow dash-line: GSC. (C) In wild type GSCs, large majority of spectrosomes were mobile and located basally (39%) during interphase. In DSas4-mut GSCs, majority of spectrosomes were stationary and located apically (54%). Wild type: n = 23, DSas4-mut: n = 24. (D)DSas4-mut GSCs had higher percentage of spectrosomes migrating from apical to the basal side prior to mitosis. Spectrosome switches are categorized as such if they migrate within 30 mins prior to mitosis (identified by nuclear envelope breakdown).
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pone.0123294.g002: Dynamic migration patterns of spectrosomes are quantified utilizing time-lapse live-imaging.(A) Spectrosome localization in DSas4-mut becomes predominantly apical compared to wild type. #: p<0.05. (B) Live image sequences shows apically (to the hub cells) migrating spectrosome in a dividing DSas4-mut GSC. Arrowhead: spectrosome. *: hub cells. Yellow dash-line: GSC. (C) In wild type GSCs, large majority of spectrosomes were mobile and located basally (39%) during interphase. In DSas4-mut GSCs, majority of spectrosomes were stationary and located apically (54%). Wild type: n = 23, DSas4-mut: n = 24. (D)DSas4-mut GSCs had higher percentage of spectrosomes migrating from apical to the basal side prior to mitosis. Spectrosome switches are categorized as such if they migrate within 30 mins prior to mitosis (identified by nuclear envelope breakdown).

Mentions: Although previous fixed sample study showed that the spectrosome in male GSCs had higher frequency localizing at the apical cortex in DSas4-mut than that in wild type [23], the migration pattern of spectrosome remain unknown. To better understand the migration of the spectrosome, live imaging study was used to examine the movement pattern of spectrosome. Firstly, results from the live imaging show that spectrosome frequently localized to the apical region when the centrosome was knocked out in DSas4-mut (67 ± 12%, n = 24) compared with wild type (33 ± 14%, n = 23) (Fig 2A). Additionally, live imaging revealed previously undiscovered dynamic movement of spectrosome (a typical DSas4-mut GSC is shown in Fig 2B). Spectrosomes in both wild type and DSas4-mut were mobile during interphase and became immobilized prior to entering mitosis. In wild type (n = 23) GSCs, mobile and basally positioned spectrosomes composed 39%, while stationary and apically positioned spectrosomes composed 26% (Fig 2C). In DSas4-mut (n = 24) GSCs, stationary and apically positioned spectrosomes composed majority at 54%, while mobile and basally positioned spectrosomes composed 17%. Spectrosome was counted as stationary when it stays at either basal or apical ends for 30 minutes or longer. Furthermore, spectrosomes are highly positioned at the apical region (75%, 3 out of 4 GSCs) in the very rare and severely misoriented spindles in DSas4-mut GSCs, while only 54% (13 out of 24 GSCs) positioned at apical region in DSas4-mut GSCs with the properly oriented spindles. On few occasions, the apically located spectrosomes quickly migrated over to the basal location prior to mitosis (see S1 Movie) (wild type: 4%, DSas4-mut: 13%) (Fig 2D). These results demonstrate that without centrosome, majority of spectrosomes position at the apical end of the GSC and become immobilized.


Dynamic interplay of spectrosome and centrosome organelles in asymmetric stem cell divisions.

Bang C, Cheng J - PLoS ONE (2015)

Dynamic migration patterns of spectrosomes are quantified utilizing time-lapse live-imaging.(A) Spectrosome localization in DSas4-mut becomes predominantly apical compared to wild type. #: p<0.05. (B) Live image sequences shows apically (to the hub cells) migrating spectrosome in a dividing DSas4-mut GSC. Arrowhead: spectrosome. *: hub cells. Yellow dash-line: GSC. (C) In wild type GSCs, large majority of spectrosomes were mobile and located basally (39%) during interphase. In DSas4-mut GSCs, majority of spectrosomes were stationary and located apically (54%). Wild type: n = 23, DSas4-mut: n = 24. (D)DSas4-mut GSCs had higher percentage of spectrosomes migrating from apical to the basal side prior to mitosis. Spectrosome switches are categorized as such if they migrate within 30 mins prior to mitosis (identified by nuclear envelope breakdown).
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Related In: Results  -  Collection

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pone.0123294.g002: Dynamic migration patterns of spectrosomes are quantified utilizing time-lapse live-imaging.(A) Spectrosome localization in DSas4-mut becomes predominantly apical compared to wild type. #: p<0.05. (B) Live image sequences shows apically (to the hub cells) migrating spectrosome in a dividing DSas4-mut GSC. Arrowhead: spectrosome. *: hub cells. Yellow dash-line: GSC. (C) In wild type GSCs, large majority of spectrosomes were mobile and located basally (39%) during interphase. In DSas4-mut GSCs, majority of spectrosomes were stationary and located apically (54%). Wild type: n = 23, DSas4-mut: n = 24. (D)DSas4-mut GSCs had higher percentage of spectrosomes migrating from apical to the basal side prior to mitosis. Spectrosome switches are categorized as such if they migrate within 30 mins prior to mitosis (identified by nuclear envelope breakdown).
Mentions: Although previous fixed sample study showed that the spectrosome in male GSCs had higher frequency localizing at the apical cortex in DSas4-mut than that in wild type [23], the migration pattern of spectrosome remain unknown. To better understand the migration of the spectrosome, live imaging study was used to examine the movement pattern of spectrosome. Firstly, results from the live imaging show that spectrosome frequently localized to the apical region when the centrosome was knocked out in DSas4-mut (67 ± 12%, n = 24) compared with wild type (33 ± 14%, n = 23) (Fig 2A). Additionally, live imaging revealed previously undiscovered dynamic movement of spectrosome (a typical DSas4-mut GSC is shown in Fig 2B). Spectrosomes in both wild type and DSas4-mut were mobile during interphase and became immobilized prior to entering mitosis. In wild type (n = 23) GSCs, mobile and basally positioned spectrosomes composed 39%, while stationary and apically positioned spectrosomes composed 26% (Fig 2C). In DSas4-mut (n = 24) GSCs, stationary and apically positioned spectrosomes composed majority at 54%, while mobile and basally positioned spectrosomes composed 17%. Spectrosome was counted as stationary when it stays at either basal or apical ends for 30 minutes or longer. Furthermore, spectrosomes are highly positioned at the apical region (75%, 3 out of 4 GSCs) in the very rare and severely misoriented spindles in DSas4-mut GSCs, while only 54% (13 out of 24 GSCs) positioned at apical region in DSas4-mut GSCs with the properly oriented spindles. On few occasions, the apically located spectrosomes quickly migrated over to the basal location prior to mitosis (see S1 Movie) (wild type: 4%, DSas4-mut: 13%) (Fig 2D). These results demonstrate that without centrosome, majority of spectrosomes position at the apical end of the GSC and become immobilized.

Bottom Line: Utilizing time-lapse live cell imaging, customized tracking, and image processing programs, we found that most acentrosomal GSCs have the spectrosomes reposition from the basal end (wild type) to the apical end close to hub-GSC interface (acentrosomal GSCs).For acentrosomal GSCs, their mitotic spindles were still highly oriented and divided asymmetrically with longer mitosis duration, resulting in asymmetric divisions.Moreover, when the spectrosome was knocked out, the centrosomes velocity decreased and centrosomes located closer to hub-GSC interface.

View Article: PubMed Central - PubMed

Affiliation: Department of Bioengineering, The University of Illinois at Chicago, Chicago, Illinois, United States of America.

ABSTRACT
Stem cells have remarkable self-renewal ability and differentiation potency, which are critical for tissue repair and tissue homeostasis. Recently it has been found, in many systems (e.g. gut, neurons, and hematopoietic stem cells), that the self-renewal and differentiation balance is maintained when the stem cells divide asymmetrically. Drosophila male germline stem cells (GSCs), one of the best characterized model systems with well-defined stem cell niches, were reported to divide asymmetrically, where centrosome plays an important role. Utilizing time-lapse live cell imaging, customized tracking, and image processing programs, we found that most acentrosomal GSCs have the spectrosomes reposition from the basal end (wild type) to the apical end close to hub-GSC interface (acentrosomal GSCs). In addition, these apically positioned spectrosomes were mostly stationary while the basally positioned spectrosomes were mobile. For acentrosomal GSCs, their mitotic spindles were still highly oriented and divided asymmetrically with longer mitosis duration, resulting in asymmetric divisions. Moreover, when the spectrosome was knocked out, the centrosomes velocity decreased and centrosomes located closer to hub-GSC interface. We propose that in male GSCs, the spectrosome recruited to the apical end plays a complimentary role in ensuring proper spindle orientation when centrosome function is compromised.

No MeSH data available.


Related in: MedlinePlus