Food & You: A digital cohort on personalized nutrition.

Nutrition is a key contributor to health. Recently, several studies have identified associations between factors such as microbiota composition and health-related responses to dietary intake, raising the potential of personalized nutritional recommendations. To further our understanding of personalized nutrition, detailed individual data must be collected from participants in their day-to-day lives. However, this is challenging in conventional studies that require clinical measurements and site visits. So-called digital or remote cohorts allow in situ data collection on a daily basis through mobile applications, online services, and wearable sensors, but they raise questions about study retention and data quality. "Food & You" is a personalized nutrition study implemented as a digital cohort in which participants track food intake, physical activity, gut microbiota, glycemia, and other data for two to four weeks. Here, we describe the study protocol, report on study completion rates, and describe the collected data, focusing on assessing their quality and reliability. Overall, the study collected data from over 1000 participants, including high-resolution data of nutritional intake of more than 46 million kcal collected from 315,126 dishes over 23,335 participant days, 1,470,030 blood glucose measurements, 49,110 survey responses, and 1,024 stool samples for gut microbiota analysis. Retention was high, with over 60% of the enrolled participants completing the study. Various data quality assessment efforts suggest the captured high-resolution nutritional data accurately reflect individual diet patterns, paving the way for digital cohorts as a typical study design for personalized nutrition.

Conserved domains control heterochromatin localization and silencing properties of SU(VAR)3-7.

The Drosophila protein SU(VAR)3-7 is essential for fly viability, chromosome structure, and heterochromatin formation. We report that searches in silico and in vitro for homologues of SU(VAR)3-7 were successful within, but not outside, the Drosophila genus. Protein sequence homology between the distant sibling species Drosophila melanogaster and Drosophila virilis is low, except for the general organization of the protein and three conserved motives: seven widely spaced zinc fingers in the N-terminal half and the BESS and BoxA motives in the C-terminal half of the protein. We have undertaken a fine functional dissection of SU(VAR)3-7 in vivo using transgenes encoding truncations of the protein. BESS mediates interaction of SU(VAR)3-7 with itself, and BoxA is required for specific heterochromatin association. Both are necessary for the silencing properties of SU(VAR)3-7. The seven zinc fingers, widely spaced over the N-terminal half of SU(VAR)3-7, are required for binding to polytene chromosomes. One finger is necessary and sufficient to determine the appropriate chromatin association of the C-terminal half of the protein. Conferring a function to each of the conserved motives allows us to better understand the mode of action of SU(VAR)3-7 in triggering heterochromatin formation and subsequent genomic silencing.

Increased expression of Drosophila Su(var)3-7 triggers Su(var)3-9-dependent heterochromatin formation.

The Su(var)3-7 protein is essential for fly viability, and several lines of evidence support its key importance in heterochromatin formation: it binds to pericentric heterochromatin, it potently suppresses variegation and it interacts with HP1. However, the mode of action of Su(var)3-7 is poorly understood. Here we investigate in vivo the consequences of increased Su(var)3-7 expression on fly viability and chromatin structure. A large excess of Su(var)3-7 induces lethality, whereas lower doses permit survival and cause spectacular changes in the morphology of polytene chromosomes in males, and to a lesser extent in females. The male X is always the most affected chromosome: it becomes highly condensed and shortened, and its characteristic banding pattern is modified. In addition, Su(var)3-7 was found over the complete length of all chromosomes. This event coincides with the appearance of heterochromatin markers such as histone H3K9 dimethylation and HP1 at many sites on autosomes and, more strikingly, on the male X chromosome. These two features are strictly dependent on the histone-methyltransferase Su(var)3-9, whereas the generalised localisation of Su(var)3-7 is not. These data provide evidence for a dose-dependent regulatory role of Su(var)3-7 in chromosome morphology and heterochromatin formation. Moreover they show that Su(var)3-7 expression is sufficient to induce Su(var)3-9-dependent ectopic heterochromatinisation and suggest a functional link between Su(var)3-7 and the histone-methyltransferase Su(var)3-9.

Functional dissection of the Drosophila modifier of variegation Su(var)3-7.

An increase in the dose of the heterochromatin-associated Su(var)3-7 protein of Drosophila augments the genomic silencing of position-effect variegation. We have expressed a number of fragments of the protein in flies to assign functions to the different domains. Specific binding to pericentric heterochromatin depends on the C-terminal half of the protein. The N terminus, containing six of the seven widely spaced zinc fingers, is required for binding to bands on euchromatic arms, with no preference for pericentric heterochromatin. In contrast to the enhancing properties of the full-length protein, the N terminus half has no effect on heterochromatin-dependent position-effect variegation. In contrast, the C terminus moiety suppresses variegation. This dominant negative effect on variegation could result from association of the fragment with the wild type endogenous protein. Indeed, we have found and mapped a domain of self-association in this C-terminal half. Furthermore, a small fragment of the C-terminal region actually depletes pericentric heterochromatin from endogenous Su(var)3-7 and has a very strong suppressor effect. This depletion is not followed by a depletion of HP1, a companion of Su(var)3-7. This indicates that Su(var)3-7 does not recruit HP1 to heterochromatin. We propose in conclusion that the association of Su(var)3-7 to heterochromatin depends on protein-protein interaction mediated by the C-terminal half of the sequence, while the silencing function requires also the N-terminal half containing the zinc fingers.

Isolation of Su(var)3-7 mutations by homologous recombination in Drosophila melanogaster.

The Su(var)3-7 gene, a haplo-suppressor and triplo-enhancer of position-effect variegation (PEV), encodes a zinc finger heterochromatin-associated protein. To understand the role of this protein in heterochromatin and genomic silencing, mutations were generated by homologous recombination. The donor fragment contained a yellow(+) gene and 7.6 kb of the Su(var)3-7 gene inserted between two FRTs. The Su(var)3-7 sequence contained three stop codons flanking an I-SceI cut site located in the 5' half of the gene. Using two different screening approaches, we obtained an allelic series composed of three mutant alleles. The three mutations are dominant suppressors of PEV. One behaves as a null mutation and results in a maternal-effect recessive lethal phenotype that can be rescued by a zygotic paternal wild-type gene. A P transposon zygotically expressing a Su(var)3-7 full-length cDNA also rescues the mutant phenotype. One hypomorphic allele is viable and the pleiotropic phenotype showed by adult flies indicates that rapidly and late dividing cells seem the most affected by reduced amounts of Su(var)3-7 protein. All three mutants were characterized at the molecular level. Each expresses a portion of the Su(var)3-7 protein that is unable to enter the nucleus and bind chromatin.