A common variant of the latrophilin 3 gene, LPHN3, confers susceptibility to ADHD and predicts effectiveness of stimulant medication.

Attention-Deficit/Hyperactivity Disorder (ADHD) has a very high heritability (0.8), suggesting that about 80% of phenotypic variance is due to genetic factors. We used the integration of statistical and functional approaches to discover a novel gene that contributes to ADHD. For our statistical approach, we started with a linkage study based on large multigenerational families in a population isolate, followed by fine mapping of targeted regions using a family-based design. Family- and population-based association studies in five samples from disparate regions of the world were used for replication. Brain imaging studies were performed to evaluate gene function. The linkage study discovered a genome region harbored in the Latrophilin 3 gene (LPHN3). In the world-wide samples (total n=6360, with 2627 ADHD cases and 2531 controls) statistical association of LPHN3 and ADHD was confirmed. Functional studies revealed that LPHN3 variants are expressed in key brain regions related to attention and activity, affect metabolism in neural circuits implicated in ADHD, and are associated with response to stimulant medication. Linkage and replicated association of ADHD with a novel non-candidate gene (LPHN3) provide new insights into the genetics, neurobiology, and treatment of ADHD.

Clinical spectrum of SIX3-associated mutations in holoprosencephaly: correlation between genotype, phenotype and function.

BACKGROUND: Holoprosencephaly (HPE) is the most common structural malformation of the human forebrain. There are several important HPE mutational target genes, including the transcription factor SIX3, which encodes an early regulator of Shh, Wnt, Bmp and Nodal signalling expressed in the developing forebrain and eyes of all vertebrates. OBJECTIVE: To characterise genetic and clinical findings in patients with SIX3 mutations. METHODS: Patients with HPE and their family members were tested for mutations in HPE-associated genes and the genetic and clinical findings, including those for additional cases found in the literature, were analysed. The results were correlated with a mutation-specific functional assay in zebrafish. RESULTS: In a cohort of patients (n = 800) with HPE, SIX3 mutations were found in 4.7% of probands and additional cases were found through testing of relatives. In total, 138 cases of HPE were identified, 59 of whom had not previously been clinically presented. Mutations in SIX3 result in more severe HPE than in other cases of non-chromosomal, non-syndromic HPE. An over-representation of severe HPE was found in patients whose mutations confer greater loss of function, as measured by the functional zebrafish assay. The gender ratio in this combined set of patients was 1.5:1 (F:M) and maternal inheritance was almost twice as common as paternal. About 14% of SIX3 mutations in probands occur de novo. There is a wide intrafamilial clinical range of features and classical penetrance is estimated to be at least 62%. CONCLUSIONS: Our data suggest that SIX3 mutations result in relatively severe HPE and that there is a genotype-phenotype correlation, as shown by functional studies using animal models.

Pattern of fecal endogenous nitrogen excretion in rats fed leguminous diets.

The main objective of this investigation was to establish the pattern in relation to time of the rat fecal endogenous nitrogen excretion by continuous feeding of balanced diets containing common peas, cowpeas or common beans as the protein sources (10% protein), labeled with 1.000 atoms % of 15N-excess. Nitrogen of endogenous origin was measured by the isotope dilution method in a 6-day experiment. Fecal excretion of endogenous nitrogen of rats fed the leguminous diets was roughly twice that of rats fed the non-protein diet (88 mg, 42 mg), and the excretion of total fecal nitrogen did not differ among leguminous diets. From the third to the sixth day of the experiment, the endogenous nitrogen excretion, either as a percentage of quantity (mg), attained a statistically non different value (p > 0.05). A common pattern of excretion of fecal endogenous nitrogen as a function of time was expressed by a strong negative (r < -0.95) power regression (y = A.x-B) for the common pea, the cowpea or the common bean diets. Conversely, the excretion of dietary nitrogen did not show a common pattern as a function of time for all experimental diets.

The use of nitrogen-15 labeling for the assessment of leguminous protein digestibility.

This study evaluated the digestibility of leguminous protein labeled with 15N, by using nitrogen balance and quantitation of fecal endogenous nitrogen (FEN), determined by isotopic dilution, in order to correct apparent values. Seeds of common beans, cowpea and common pea labeled with 1.000 atoms% of 15N-excess were used as protein sources in diets for 60 male Wistar rats, during a 6-day assay. The real digestibility values obtained with FEN were 77.6, 84.4, and 86.3% for common beans, cowpea and common pea, respectively. They were higher and statistically different (p < 0.05) than true digestibility values, corrected by non-protein diet. FEN showed a direct, moderate and positive relation with weight of dry matter eaten, initial body weight, weight gain and weight of dry matter of feces, the latter showing the highest correlation, with a coefficient r = 0.8930 at 1% level.