Mouse ultrasonic vocalisations have been often used as a paradigm to extrapolate 
vocal communication defects observed in patients with autism spectrum disorders 
(ASD). The role of these vocalisations as well as their development, structure 
and informational content, however, remain largely unknown. In the present 
study, we characterised in depth the emission of pup and adult ultrasonic 
vocalisations of wild-type mice and their ProSAP1/Shank2(-/-) littermates 
lacking a synaptic scaffold protein mutated in ASD. We hypothesised that the 
vocal behaviour of ProSAP1/Shank2(-/-) mice not only differs from the vocal 
behaviour of their wild-type littermates in a quantitative way, but also 
presents more qualitative abnormalities in temporal organisation and acoustic 
structure. We first quantified the rate of emission of ultrasonic vocalisations, 
and analysed the organisation of vocalisations sequences using Markov models. We 
subsequently measured duration and peak frequency characteristics of each 
ultrasonic vocalisation, to characterise their acoustic structure. In wild-type 
mice, we found a high level of organisation in sequences of ultrasonic 
vocalisations, suggesting a communicative function in this complex system. Very 
limited significant sex-related variations were detected in their usage and 
acoustic structure, even in adult mice. In adult ProSAP1/Shank2(-/-) mice, we 
found abnormalities in the call usage and the structure of ultrasonic 
vocalisations. Both ProSAP1/Shank2(-/-) male and female mice uttered less 
vocalisations with a different call distribution and at lower peak frequency in 
comparison with wild-type littermates. This study provides a comprehensive 
framework to characterise abnormalities of ultrasonic vocalisations in mice and 
confirms that ProSAP1/Shank2(-/-) mice represent a relevant model to study 
communication defects.