Pitt-Hopkins Mouse Model has Altered Particular Gastrointestinal Transits In Vivo

Abstract

Pitt-Hopkins syndrome (PTHS) is a neurodevelopmental disorder, classified as an autism spectrum disorder that is caused by the haploinsufficiency of Transcription Factor 4 (TCF4). The most common non-neurological symptoms in PTHS patients are gastrointestinal (GI) disturbances, mainly gastroesophageal reflux and severe constipation (in about 30 and 75% of PTHS patients, respectively). We hypothesized that the recently recognized mouse model of PTHS will exhibit problems with their gut function. We conducted series of in vivo tests on 15- to 19- week old male mice, heterozygous for the TCF4 functional deletion, mimicking the TCF4 haploinsufficiency in PTHS patients, and their wild type littermates. Data collection and initial analysis were performed blindly, that is, the genotyping key was received after the mean values were calculated for each individual animal, and then mean/median of each group was subsequently calculated. Body weight, fecal pellet output, and fluid content were similar between the groups, indicating normal gross growth of PTHS mice and their overall physiological GI motility and intestinal secretion/absorption. There were no significant differences in gut length and gross appearance pointing out that PTHS mice have normal gut in gross anatomical terms. However, the assessment of gut transit indicates that, while whole-gut transit velocity was similar between the groups, the upper GI and distal colon transit velocities were significantly reduced in the PTHS mice. This is the first evidence of specific gut related problems in the PTHS mice. Our study also validates the TCF4 functional knockout mice as an animal model to study PTHS-associated GI disturbances.

Keywords: E2-2; ITF2; PTHS mouse model; TCF4; gut transit.

Figure 1

Pitt–Hopkins syndrome (PTHS) mice have normal body mass and pellet output in vivo. (A) Body weights. Wild type (wt) and PTHS mice have similar body weights. (B–D) Pellet production and composition. PTHS and wt animals do not differ significantly in the total number of pellets (B), pellet wet/dry weight (C, left/right) and pellet fluid content (D). Data are shown as mean ± standard error of mean (SEM) in A, B and D; or as median ± interquartile range (IQR) in C. Sample sizes were the same for all measurements: 18 and 16 mice for wt and PTHS groups, respectively.

Figure 2

Particular in vivo gut transit velocities are reduced in PTHS mice. (A) Lengths of intestines. Total (left), small (center) and large (right) intestines were similar in length between the wt and PTHS animals. (B) Gastrointestinal (GI) transit velocities in vivo. Whole-gut transit velocity (left) was similar between the groups. Upper GI (center) and distal colon (right) transit velocities were significantly reduced in the PTHS mice.^*P < 0.05, Student’s t-test and Mann–Whitney U-test, respectively. Data are shown as mean ± SEM (left and center graphs) or as median ± IQR (right graphs). 18 wt and 16 PTHS mice were used for all the measurements except the upper GI transit. Three animals were excluded from the analysis of the upper GI transit, 1 in wt and 2 in PTHS groups, due to obvious distress signs after the gavage.