Timing the onset of metamorphosis in Drosophila

Because Drosophila do not grow after initiation of metamorphosis, their final body size is determined by larval growth rate and duration of the larval growth phase. Drosophila metamorphosis is triggered by the steroid hormone ecdysone, which is produced in the prothoracic gland (PG). Ecdysone synthesis requires expression of the "Halloween" genes, which encode ecdysone biosynthetic enzymes. Growth rate is regulated by Insulin-like peptides, which are released from the insulin-producing cells (IPCs). Genetic ablation of the IPCs decreases growth rate and delays onset of metamorphosis, suggesting that ecdysone synthesis is induced by insulin signaling. Inhibiting PI3 Kinase (PI3K), the major effector of insulin signaling, in the PG similarly delays metamorphosis as a consequence of decreased ecdysone synthesis and decreased Halloween gene expression. In contrast, activating PI3K in the PG advances the onset of metamorphosis and increases Halloween gene expression. Here I report that increased insulin signaling, accomplished inhibiting the protein kinase A pathway in the IPCs increases insulin signaling and increases growth rate but also advances the onset of metamorphosis by increasing expression of at least one Halloween gene. Ecdysone synthesis is promoted by a second peptide hormone, PTTH, which activates Halloween gene expression via the Torso receptor followed by Ras and Raf in the PG. Null mutations in the transcription factor broad (br ) prevent torso transcription and thus prevent Halloween gene expression and metamorphosis. Here I identify Br as the mechanistic link between PI3K activity and Halloween gene expression. I found that PI3K activity is required for br expression by inhibiting the downstream kinase GSK-3. I provide evidence that three nuclear hormone receptors, βFTZ-F1, HR3 and E75, link GSK-3 activity with br expression: RNAi-mediated βFTZ-F1 or HR3 knockdown, or E75A overexpression, in the PG prevents br expression. I also found that ectopic Torso pathway activation, accomplished by expressing the constitutively active Rafgof , restores Halloween gene transcription to larvae lacking br or βFTZ-F1 , suggesting that these larvae fail to express Halloween genes because they fail to transcribe torso . These studies identify a potential molecular mechanism linking growth rate with competence to respond to the PITH metamorphic signal and thus initiate metamorphosis

Who is a tired student? Fatigue and its predictors from a gender perspective.

The level of fatigue among medical students is increasing. Exhaustion is an essential symptom of burnout, which may occur even while a student. Our exploratory study sought to identify the characteristics of tired students and to describe factors determining fatigue among medical students. The studied group consisted of second-year medical students (N=193) from a Polish medical university. Statistically significant differences in fatigue appeared between male and female students. We obtained positive correlations between intensity of fatigue and sleepiness, pain intensity, stress, anxiety, depression and negative health conditions, life satisfaction, emotional stability, conscientiousness, and self-efficacy. Predictors relevant for female fatigue were sleepiness, health condition, depression, and conscientiousness (the whole model explains 46% of variance in fatigue). Predictors relevant for male fatigue were sleepiness, health condition, anxiety, and agreeableness (the whole model explains 55% of variance in fatigue). We did not observe differences in fatigue between sleepless, overloaded, or stressed people. Explaining the differences between male and female predictors and levels of fatigue in terms of personality traits through the prism of defined stereotypical social roles is worth considering

Loss-of-function mutations in Lysyl-tRNA synthetase cause various leukoencephalopathy phenotypes

Objective: To expand the clinical spectrum of lysyl-tRNA synthetase (KARS) gene–related diseases, which so far includes Charcot-Marie-Tooth disease, congenital visual impairment and microcephaly, and nonsyndromic hearing impairment. Methods: Whole-exome sequencing was performed on index patients from 4 unrelated families with leukoencephalopathy. Candidate pathogenic variants and their cosegregation were confirmed by Sanger sequencing. Effects of mutations on KARS protein function were examined by aminoacylation assays and yeast complementation assays. Results: Common clinical features of the patients in this study included impaired cognitive ability, seizure, hypotonia, ataxia, and abnormal brain imaging, suggesting that the CNS involvement is the main clinical presentation. Six previously unreported and 1 known KARS mutations were identified and cosegregated in these families. Two patients are compound heterozygous for missense mutations, 1 patient is homozygous for a missense mutation, and 1 patient harbored an insertion mutation and a missense mutation. Functional and structural analyses revealed that these mutations impair aminoacylation activity of lysyl-tRNA synthetase, indicating that de- fective KARS function is responsible for the phenotypes in these individuals. Conclusions: Our results demonstrate that patients with loss-of-function KARS mutations can manifest CNS disorders, thus broadening the phenotypic spectrum associated with KARS-related disease

Phenotypic and molecular characterisation of CDK13-related congenital heart defects, dysmorphic facial features and intellectual developmental disorders

Background: De novo missense variants in CDK13 have been described as the cause of syndromic congenital heart defects in seven individuals ascertained from a large congenital cardiovascular malformations cohort. We aimed to further define the phenotypic and molecular spectrum of this newly described disorder. Methods: To minimise ascertainment bias, we recruited nine additional individuals with CDK13 pathogenic variants from clinical and research exome laboratory sequencing cohorts. Each individual underwent dysmorphology exam and comprehensive medical history review. Results: We demonstrate greater than expected phenotypic heterogeneity, including 33% (3/9) of individuals without structural heart disease on echocardiogram. There was a high penetrance for a unique constellation of facial dysmorphism and global developmental delay, as well as less frequently seen renal and sacral anomalies. Two individuals had novel CDK13 variants (p.Asn842Asp, p.Lys734Glu), while the remaining seven unrelated individuals had a recurrent, previously published p.Asn842Ser variant. Summary of all variants published to date demonstrates apparent restriction of pathogenic variants to the protein kinase domain with clustering in the ATP and magnesium binding sites. Conclusions: Here we provide detailed phenotypic and molecular characterisation of individuals with pathogenic variants in CDK13 and propose management guidelines based upon the estimated prevalence of anomalies identified. Keywords: CDK13, CHDFIDD, De novo variant, Neurodevelopmental disorders, Agenesis of the corpus callosum, Hypertelorism, Developmental delay, Cyclin-dependent kinase, Undiagnosed Diseases Networ

Phenotypic expansion in DDX3X - a common cause of intellectual disability in females

De novo variants in DDX3X account for 1-3% of unexplained intellectual disability (ID) cases and are amongst the most common causes of ID especially in females. Forty-seven patients (44 females, 3 males) have been described. We identified 31 additional individuals carrying 29 unique DDX3X variants, including 30 postnatal individuals with complex clinical presentations of developmental delay or ID, and one fetus with abnormal ultrasound findings. Rare or novel phenotypes observed include respiratory problems, congenital heart disease, skeletal muscle mitochondrial DNA depletion, and late-onset neurologic decline. Our findings expand the spectrum of DNA variants and phenotypes associated with DDX3X disorders

Human Dectin-1 Deficiency Impairs Macrophage-Mediated Defense Against Phaeohyphomycosis

Subcutaneous phaeohyphomycosis typically affects immunocompetent individuals following traumatic inoculation. Severe or disseminated infection can occur in CARD9 deficiency or after transplantation, but the mechanisms protecting against phaeohyphomycosis remain unclear. We evaluated a patient with progressive, refractory Corynespora cassiicola phaeohyphomycosis and found that he carried biallelic deleterious mutations in CLEC7A encoding the CARD9-coupled, β-glucan-binding receptor, Dectin-1. The patient\u27s PBMCs failed to produce TNF-α and IL-1β in response to β-glucan and/or C. cassiicola. To confirm the cellular and molecular requirements for immunity against C. cassiicola, we developed a mouse model of this infection. Mouse macrophages required Dectin-1 and CARD9 for IL-1β and TNF-α production, which enhanced fungal killing in an interdependent manner. Deficiency of either Dectin-1 or CARD9 was associated with more severe fungal disease, recapitulating the human observation. Because these data implicated impaired Dectin-1 responses in susceptibility to phaeohyphomycosis, we evaluated 17 additional unrelated patients with severe forms of the infection. We found that 12 out of 17 carried deleterious CLEC7A mutations associated with an altered Dectin-1 extracellular C-terminal domain and impaired Dectin-1-dependent cytokine production. Thus, we show that Dectin-1 and CARD9 promote protective TNF-α- and IL-1β-mediated macrophage defense against C. cassiicola. More broadly, we demonstrate that human Dectin-1 deficiency may contribute to susceptibility to severe phaeohyphomycosis by certain dematiaceous fungi