Fig. 4: CSF TTR is dynamic across the day.

a Schematic of the freely-moving photometry setup, consisting of a 470 nm LED light source, CMOS camera for signal collection, and patch cord to the animal. Inset shows the geometry of the optical fiber in the cannula relative to the ventricular system of the mouse. b Overview of all summarized photometry recordings, with each bar indicating the start (on the left) and stop times (three animals recorded simultaneously in each recording). The first 8 h (light-dark transition) of both the light–dark and dark-dark recordings were combined for analyses and subsequently treated separately for the later periods when the light patterns were distinct. Two Ttr^mNeonGreen and one wild-type animal were excluded from analysis for health reasons. c Summary of all Ttr^mNeonGreen and wild-type recordings in the first 8-h period around the first lights-off. N = 25 biologically independent Ttr^mNeonGreen animals across seven independent experiments and N = 5 biologically independent wild-type animals across two experiments. Data are presented as mean values ± standard error of the mean (SEM). d Peak responses, defined as the average signal over the 8:30 p.m.—9:30 p.m. interval, of all Ttr^mNeonGreen and wild-type recordings summarized in c. Horizontal lines are drawn at the minimal and maximal wild-type signals, and Ttr^mNeonGreen recordings are categorized based on these subdivisions into strong responders (top group, red), wild-type-like responders (middle group, peach), and dropping signals (bottom group, blue). e Heatmap showing each individual recording summarized in c, with subgroups color-coded as in d. Green tick marks on the heatmap indicate the times where each strongly responding trace reaches 20% of its peak signal (average between 8:30 p.m. and 9:30 p.m.). f Summary of the green tick marks in the heatmap in e, indicating that 20% peak response is reached a median of 66.9 min before lights-off. Box plots in d, f show median value at the red central bar, with the bottom and top edges of the box indicating the 25th and 75th percentiles, respectively. The whiskers extend to the most extreme values not considered outliers, and outliers (more than 1.5 times the interquartile range away from median) are plotted individually and marked with a red ‘+’ symbol. Male mice were analyzed. Source data are provided as a Source Data file (Source Data).