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The ubiquilin gene family: evolutionary patterns and functional insights.

Marín I - BMC Evol. Biol. (2014)

Bottom Line: This exceptional mammalian-specific expansion is the result of the recent emergence of four new genes, three of them (UBQLN3, UBQLN5 and UBQLNL) with precise testis-specific expression patterns that indicate roles in the postmeiotic stages of spermatogenesis.The ubiquilin gene family is highly conserved in eukaryotes.The infrequent lineage-specific amplifications observed may be linked to the emergence of novel functions in particular tissues.

View Article: PubMed Central - HTML - PubMed

Affiliation: Instituto de Biomedicina de Valencia, Consejo Superior de Investigaciones Científicas (IBV-CSIC), Valencia, Spain. imarin@ibv.csic.es.

ABSTRACT

Background: Ubiquilins are proteins that function as ubiquitin receptors in eukaryotes. Mutations in two ubiquilin-encoding genes have been linked to the genesis of neurodegenerative diseases. However, ubiquilin functions are still poorly understood.

Results: In this study, evolutionary and functional data are combined to determine the origin and diversification of the ubiquilin gene family and to characterize novel potential roles of ubiquilins in mammalian species, including humans. The analysis of more than six hundred sequences allowed characterizing ubiquilin diversity in all the main eukaryotic groups. Many organisms (e. g. fungi, many animals) have single ubiquilin genes, but duplications in animal, plant, alveolate and excavate species are described. Seven different ubiquilins have been detected in vertebrates. Two of them, here called UBQLN5 and UBQLN6, had not been hitherto described. Significantly, marsupial and eutherian mammals have the most complex ubiquilin gene families, composed of up to 6 genes. This exceptional mammalian-specific expansion is the result of the recent emergence of four new genes, three of them (UBQLN3, UBQLN5 and UBQLNL) with precise testis-specific expression patterns that indicate roles in the postmeiotic stages of spermatogenesis. A gene with related features has independently arisen in species of the Drosophila genus. Positive selection acting on some mammalian ubiquilins has been detected.

Conclusions: The ubiquilin gene family is highly conserved in eukaryotes. The infrequent lineage-specific amplifications observed may be linked to the emergence of novel functions in particular tissues.

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Related in: MedlinePlus

Expression of ubiquilin genes in particular testis samples in mouse (Panel A) and human (B). Data from Chalmel et al.[62], again in arbitrary expression units.
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Figure 9: Expression of ubiquilin genes in particular testis samples in mouse (Panel A) and human (B). Data from Chalmel et al.[62], again in arbitrary expression units.

Mentions: More precise assesment of those potential roles are provided by experiments devised to determine gene expression in particular cell types present in the testis. Figure 9 (top panel) shows microarray results measuring expression of ubiquilin genes in different cell types, seminiferous tubules and whole testis of the mouse [62]. In good agreement with the results presented above, expression of UBQLNL group genes is high in postmeiotic spermatids, but low or absent in spermatocytes, spermatogonia or somatic Sertoli cells. Actually, it is possible that the low level of expression detected for those genes in spermatocytes is due to contaminants, given that the authors describe the sample as “82.5% pure”. In any case, these results agree well with postmeiotic roles, in spermiogenesis, for the UBQLNL group genes. Results for human samples [62] are similar (Figure 9B). The relative lower levels in seminifeous tubules or whole testis when compared with mouse (Figure 9A) or with their own levels of expression in spermatids, may be due to an age-associated low content of postmeiotic germ line cells in the human individuals from which the samples were obtained, given that they were on average 77 years old.


The ubiquilin gene family: evolutionary patterns and functional insights.

Marín I - BMC Evol. Biol. (2014)

Expression of ubiquilin genes in particular testis samples in mouse (Panel A) and human (B). Data from Chalmel et al.[62], again in arbitrary expression units.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4230246&req=5

Figure 9: Expression of ubiquilin genes in particular testis samples in mouse (Panel A) and human (B). Data from Chalmel et al.[62], again in arbitrary expression units.
Mentions: More precise assesment of those potential roles are provided by experiments devised to determine gene expression in particular cell types present in the testis. Figure 9 (top panel) shows microarray results measuring expression of ubiquilin genes in different cell types, seminiferous tubules and whole testis of the mouse [62]. In good agreement with the results presented above, expression of UBQLNL group genes is high in postmeiotic spermatids, but low or absent in spermatocytes, spermatogonia or somatic Sertoli cells. Actually, it is possible that the low level of expression detected for those genes in spermatocytes is due to contaminants, given that the authors describe the sample as “82.5% pure”. In any case, these results agree well with postmeiotic roles, in spermiogenesis, for the UBQLNL group genes. Results for human samples [62] are similar (Figure 9B). The relative lower levels in seminifeous tubules or whole testis when compared with mouse (Figure 9A) or with their own levels of expression in spermatids, may be due to an age-associated low content of postmeiotic germ line cells in the human individuals from which the samples were obtained, given that they were on average 77 years old.

Bottom Line: This exceptional mammalian-specific expansion is the result of the recent emergence of four new genes, three of them (UBQLN3, UBQLN5 and UBQLNL) with precise testis-specific expression patterns that indicate roles in the postmeiotic stages of spermatogenesis.The ubiquilin gene family is highly conserved in eukaryotes.The infrequent lineage-specific amplifications observed may be linked to the emergence of novel functions in particular tissues.

View Article: PubMed Central - HTML - PubMed

Affiliation: Instituto de Biomedicina de Valencia, Consejo Superior de Investigaciones Científicas (IBV-CSIC), Valencia, Spain. imarin@ibv.csic.es.

ABSTRACT

Background: Ubiquilins are proteins that function as ubiquitin receptors in eukaryotes. Mutations in two ubiquilin-encoding genes have been linked to the genesis of neurodegenerative diseases. However, ubiquilin functions are still poorly understood.

Results: In this study, evolutionary and functional data are combined to determine the origin and diversification of the ubiquilin gene family and to characterize novel potential roles of ubiquilins in mammalian species, including humans. The analysis of more than six hundred sequences allowed characterizing ubiquilin diversity in all the main eukaryotic groups. Many organisms (e. g. fungi, many animals) have single ubiquilin genes, but duplications in animal, plant, alveolate and excavate species are described. Seven different ubiquilins have been detected in vertebrates. Two of them, here called UBQLN5 and UBQLN6, had not been hitherto described. Significantly, marsupial and eutherian mammals have the most complex ubiquilin gene families, composed of up to 6 genes. This exceptional mammalian-specific expansion is the result of the recent emergence of four new genes, three of them (UBQLN3, UBQLN5 and UBQLNL) with precise testis-specific expression patterns that indicate roles in the postmeiotic stages of spermatogenesis. A gene with related features has independently arisen in species of the Drosophila genus. Positive selection acting on some mammalian ubiquilins has been detected.

Conclusions: The ubiquilin gene family is highly conserved in eukaryotes. The infrequent lineage-specific amplifications observed may be linked to the emergence of novel functions in particular tissues.

Show MeSH
Related in: MedlinePlus