SUMMARYProtein kinase A (PKA) is an evolutionarily conserved negative regulator of the hedgehog (Hh) signal transduction pathway. PKA is known to be required for the proteolytic processing event that generates the repressor forms of the Ci and Gli transcription factors that keep target genes off in the absence of Hh. Here, we show that complete loss of PKA activity in the mouse leads to midgestation lethality and a completely ventralized neural tube, demonstrating that PKA is as strong a negative regulator of the sonic hedgehog (Shh) pathway as patched 1 (Ptch1) or suppressor of fused (Sufu). Genetic analysis shows that although PKA is important for production of the repressor form of Gli3, the principal function of PKA in the Shh pathway in neural development is to restrain activation of Gli2. Activation of the Hh pathway in PKA mutants depends on cilia, and the catalytic and regulatory subunits of PKA are localized to a compartment at the base of the primary cilia, just proximal to the basal body. The data show that PKA does not affect cilia length or trafficking of smoothened (Smo) in the cilium. Instead, we find that there is a significant increase in the level of Gli2 at the tips of cilia of PKA-null cells. The data suggest a model in which PKA acts at the base of the cilium after Gli proteins have transited the primary cilium; in this model the sequential movement of Gli proteins between compartments in the cilium and at its base controls accessibility of Gli proteins to PKA, which determines the fates of Gli proteins and the activity of the Shh pathway.

Retinitis pigmentosa (RP), the main cause of adult blindness, is a genetically heterogeneous disorder characterized by progressive loss of photoreceptors through apoptosis. Up to now, 39 genes and loci have been implicated in nonsyndromic RP, yet the genetic bases of >50% of the cases, particularly of the recessive forms, remain unknown. Previous linkage analysis in a Spanish consanguineous family allowed us to define a novel autosomal recessive RP (arRP) locus, RP26, within an 11-cM interval (17.4 Mb) on 2q31.2-q32.3. In the present study, we further refine the RP26 locus down to 2.5 Mb, by microsatellite and single-nucleotide polymorphism (SNP) homozygosity mapping. After unsuccessful mutational analysis of the nine genes initially reported in this region, a detailed gene search based on expressed-sequence-tag data was undertaken. We finally identified a novel gene encoding a ceramide kinase (CERKL), which encompassed 13 exons. All of the patients from the RP26 family bear a homozygous mutation in exon 5, which generates a premature termination codon. The same mutation was also characterized in another, unrelated, Spanish pedigree with arRP. Human CERKL is expressed in the retina, among other adult and fetal tissues. A more detailed analysis by in situ hybridization on adult murine retina sections shows expression of Cerkl in the ganglion cell layer. Ceramide kinases convert the sphingolipid metabolite ceramide into ceramide-1-phosphate, both key mediators of cellular apoptosis and survival. Ceramide metabolism plays an essential role in the viability of neuronal cells, the membranes of which are particularly rich in sphingolipids. Therefore, CERKL deficiency could shift the relative levels of the signaling sphingolipid metabolites and increase sensitivity of photoreceptor and other retinal cells to apoptotic stimuli. This is the first genetic report suggesting a direct link between retinal neurodegeneration in RP and sphingolipid-mediated apoptosis.

BackgroundA 12-week, double-blind, parallel, multi-center randomized controlled trial in 316 adult patients with major depressive disorder (MDD) was conducted to evaluate the effectiveness of pharmacogenetic (PGx) testing for drug therapy guidance.MethodsPatients with a CGI-S ≥ 4 and requiring antidepressant medication de novo or changes in their medication regime were recruited at 18 Spanish public hospitals, genotyped with a commercial PGx panel (Neuropharmagen®), and randomized to PGx-guided treatment (n = 155) or treatment as usual (TAU, control group, n = 161), using a computer-generated random list that locked or unlocked psychiatrist access to the results of the PGx panel depending on group allocation. The primary endpoint was the proportion of patients achieving a sustained response (Patient Global Impression of Improvement, PGI-I ≤ 2) within the 12-week follow-up. Patients and interviewers collecting the PGI-I ratings were blinded to group allocation. Between-group differences were evaluated using χ2-test or t-test, as per data type.ResultsTwo hundred eighty patients were available for analysis at the end of the 12-week follow-up (PGx n = 136, TAU n = 144). A difference in sustained response within the study period (primary outcome) was not observed (38.5% vs 34.4%, p = 0.4735; OR = 1.19 [95%CI 0.74-1.92]), but the PGx-guided treatment group had a higher responder rate compared to TAU at 12 weeks (47.8% vs 36.1%, p = 0.0476; OR = 1.62 [95%CI 1.00-2.61]), and this difference increased after removing subjects in the PGx-guided group when clinicians explicitly reported not to follow the test recommendations (51.3% vs 36.1%, p = 0.0135; OR = 1.86 [95%CI 1.13-3.05]). Effects were more consistent in patients with 1–3 failed drug trials. In subjects reporting side effects burden at baseline, odds of achieving a better tolerability (Frequency, Intensity and Burden of Side Effects Rating Burden subscore ≤2) were higher in the PGx-guided group than in controls at 6 weeks and maintained at 12 weeks (68.5% vs 51.4%, p = 0.0260; OR = 2.06 [95%CI 1.09-3.89]).ConclusionsPGx-guided treatment resulted in significant improvement of MDD patient’s response at 12 weeks, dependent on the number of previously failed medication trials, but not on sustained response during the study period. Burden of side effects was also significantly reduced.Trial registrationEuropean Clinical Trials Database 2013-002228-18, registration date September 16, 2013; ClinicalTrials.gov NCT02529462, retrospectively registered: August 19, 2015.Electronic supplementary materialThe online version of this article (doi:10.1186/s12888-017-1412-1) contains supplementary material, which is available to authorized users.

BackgroundSonic hedgehog (Shh) signaling in the mouse requires the microtubule-based organelle, the primary cilium. The primary cilium is assembled and maintained through the process of intraflagellar transport (IFT) and the response to Shh is blocked in mouse mutants that lack proteins required for IFT. Although the phenotypes of mouse IFT mutants do not overlap with phenotypes of known Wnt pathway mutants, recent studies report data suggesting that the primary cilium modulates responses to Wnt signals.Methodology/Principal FindingsWe therefore carried out a systematic analysis of canonical Wnt signaling in mutant embryos and cells that lack primary cilia because of loss of the anterograde IFT kinesin-II motor (Kif3a) or IFT complex B proteins (Ift172 or Ift88). We also analyzed mutant embryos with abnormal primary cilia due to defects in retrograde IFT (Dync2h1). The mouse IFT mutants express the canonical Wnt target Axin2 and activate a transgenic canonical Wnt reporter, BAT-gal, in the normal spatial pattern and to the same quantitative level as wild type littermates. Similarly, mouse embryonic fibroblasts (MEFs) derived from IFT mutants respond normally to added Wnt3a. The switch from canonical to non-canonical Wnt also appears normal in IFT mutant MEFs, as both wild-type and mutant cells do not activate the canonical Wnt reporter in the presence of both Wnt3a and Wnt5a.ConclusionsWe conclude that loss of primary cilia or defects in retrograde IFT do not affect the response of the midgestation embryo or embryo-derived fibroblasts to Wnt ligands.

Background: Annotations of completely sequenced genomes reveal that nearly half of the genes identified are of unknown function, and that some belong to uncharacterized gene families. To help resolve such issues, information can be obtained from the comparative analysis of homologous genes in model organisms.