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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 mouse testis, at different days post partum. Data, in arbitrary expression units, derived from Schultz et al.[58](Panel A), Shima et al.[59](Panel B) and Laiho et al.[60] (Panel C).
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Figure 8: Expression of ubiquilin genes in mouse testis, at different days post partum. Data, in arbitrary expression units, derived from Schultz et al.[58](Panel A), Shima et al.[59](Panel B) and Laiho et al.[60] (Panel C).

Mentions: The discovery that the UBQLNL group gens are testis-specific deserves more detailed explorations. Several works have examined how gene expression changes in mouse testis after birth. Given that meiosis starts in the mouse about 10 days post partum, it is possible to indirectly assess whether testis-specific genes may be involved in pre- or postmeiotic roles by analyzing the first wave of mouse spermatogenesis, which is highly synchronic. Figure 8 summarizes results from three studies [58-60]. Although the first two are based on expression microarrays and the third one on deep transcriptome sequencing, the results coincide, and also agree well with those shown before in Figure 6. A summary is as follows: 1) UBQLN1 has a relatively small but consistent expression in testis, from birth to adult mouse. This agrees with the data shown above in Figure 6 and also with a report indicating potential roles of UBQLN1 in spermatogenesis [61]; 2) UBQLN2 and UBQLN4 are expressed at very low/ levels in testis (actually, the background levels observed are equivalent to those found for genes considered not expressed at all in that tissue [58,59]); 3) As already detected in the global results shown above (Table 1 and Figure 6), the three UBQLNL group genes are consistently expressed in the testis, with UBQLN3 having the highest expression in the only study in which all of them were examined [60]; finally, 4) The expression of the UBQLNL group genes starts only after 20 days post partum, indicating that their products may have postmeiotic roles.


The ubiquilin gene family: evolutionary patterns and functional insights.

Marín I - BMC Evol. Biol. (2014)

Expression of ubiquilin genes in mouse testis, at different days post partum. Data, in arbitrary expression units, derived from Schultz et al.[58](Panel A), Shima et al.[59](Panel B) and Laiho et al.[60] (Panel C).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 8: Expression of ubiquilin genes in mouse testis, at different days post partum. Data, in arbitrary expression units, derived from Schultz et al.[58](Panel A), Shima et al.[59](Panel B) and Laiho et al.[60] (Panel C).
Mentions: The discovery that the UBQLNL group gens are testis-specific deserves more detailed explorations. Several works have examined how gene expression changes in mouse testis after birth. Given that meiosis starts in the mouse about 10 days post partum, it is possible to indirectly assess whether testis-specific genes may be involved in pre- or postmeiotic roles by analyzing the first wave of mouse spermatogenesis, which is highly synchronic. Figure 8 summarizes results from three studies [58-60]. Although the first two are based on expression microarrays and the third one on deep transcriptome sequencing, the results coincide, and also agree well with those shown before in Figure 6. A summary is as follows: 1) UBQLN1 has a relatively small but consistent expression in testis, from birth to adult mouse. This agrees with the data shown above in Figure 6 and also with a report indicating potential roles of UBQLN1 in spermatogenesis [61]; 2) UBQLN2 and UBQLN4 are expressed at very low/ levels in testis (actually, the background levels observed are equivalent to those found for genes considered not expressed at all in that tissue [58,59]); 3) As already detected in the global results shown above (Table 1 and Figure 6), the three UBQLNL group genes are consistently expressed in the testis, with UBQLN3 having the highest expression in the only study in which all of them were examined [60]; finally, 4) The expression of the UBQLNL group genes starts only after 20 days post partum, indicating that their products may have postmeiotic roles.

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