TTLL3 Is a tubulin glycine ligase that regulates the assembly of cilia.

In most ciliated cell types, tubulin is modified by glycylation, a posttranslational modification of unknown function. We show that the TTLL3 proteins act as tubulin glycine ligases with chain-initiating activity. In Tetrahymena, deletion of TTLL3 shortened axonemes and increased their resistance to paclitaxel-mediated microtubule stabilization. In zebrafish, depletion of TTLL3 led to either shortening or loss of cilia in several organs, including the Kupffer's vesicle and olfactory placode. We also show that, in vivo, glutamic acid and glycine ligases oppose each other, likely by competing for shared modification sites on tubulin. We propose that tubulin glycylation regulates the assembly and dynamics of axonemal microtubules and acts either directly or indirectly by inhibiting tubulin glutamylation.

O-GlcNAc modifications regulate cell survival and epiboly during zebrafish development.

BACKGROUND: The post-translational addition of the monosaccharide O-linked beta-N-acetylglucosamine (O-GlcNAc) regulates the activity of a wide variety of nuclear and cytoplasmic proteins. The enzymes O-GlcNAc Transferase (Ogt) and O-GlcNAcase (Oga) catalyze, respectively, the attachment and removal of O-GlcNAc to target proteins. In adult mice, Ogt and Oga attenuate the response to insulin by modifying several components of the signal transduction pathway. Complete loss of ogt function, however, is lethal to mouse embryonic stem cells, suggesting that the enzyme has additional, unstudied roles in development. We have utilized zebrafish as a model to determine role of O-GlcNAc modifications in development. Zebrafish has two ogt genes, encoding six different enzymatic isoforms that are expressed maternally and zygotically. RESULTS: We manipulated O-GlcNAc levels in zebrafish embryos by overexpressing zebrafish ogt, human oga or by injecting morpholinos against ogt transcripts. Each of these treatments results in embryos with shortened body axes and reduced brains at 24 hpf. The embryos had 23% fewer cells than controls, and displayed increased rates of cell death as early as the mid-gastrula stages. An extensive marker analysis indicates that derivatives of three germ layers are reduced to variable extents, and the embryos are severely disorganized after gastrulation. Overexpression of Ogt and Oga delayed epiboly and caused a severe disorganization of the microtubule and actin based cytoskeleton in the extra-embryonic yolk syncytial layer (YSL). The cytoskeletal defects resemble those previously reported for embryos lacking function of the Pou5f1/Oct4 transcription factor spiel ohne grenzen. Consistent with this, Pou5f1/Oct4 is modified by O-GlcNAc in human embryonic stem cells. CONCLUSION: We conclude that O-GlcNAc modifications control the activity of proteins that regulate apoptosis and epiboly movements, but do not seem to regulate germ layer specification. O-GlcNAc modifies the transcription factor Spiel ohne grenzen/Pou5f1 and may regulate its activity.

Effects of childhood sexual abuse on neuropsychological and cognitive function in college women.

Twenty-six college women with a history of repeated childhood sexual abuse were recruited from the community and compared with 19 healthy female collegiate subjects on neurocognitive measures. Abused subjects showed increased response latency variability and diminished inhibitory capacity during a GO/NO-GO/STOP vigilance task. A strong association was found between duration of abuse and memory impairments. Math Scholastic Aptitude Test (SAT) scores were significantly lower in abused subjects when matched against comparison subjects and when compared to their own Verbal SAT scores. Childhood sexual abuse appears to be associated with a constellation of neuropsychological deficiencies even in a group of relatively healthy women.