Jane L. Hurst

Urine marking in populations of wild house mice Mus domesticus Rutty. III. Communication between the sexes

Abstract Several hypotheses were proposed for the function of urine mark communication between female house mice; predicted responses of females towards urine marks were then compared with those observed within eight captive territorial family groups. The responses of individual resident females in four classes (breeding and non-breeding adults, subadults and juveniles) were measured towards familiar resident, familiar neighbour and unfamiliar urine from breeding and subadult females, and towards a clean patch of substrate, introduced into their family-marked territory. Strong counter-marking of breeding female urine by resident breeding females especially on neighbour urine, prolonged investigation of familiar and unfamiliar urine by subadult females, and the specific attraction of resident females to neighbour female urine, support the proposal that urine marking plays an important role in communication between females. Responses were consistent with the hypothesis that females mark at high frequency to advertise their dominant breeding status to other females. The importance of such communication for the social modulation of individual breeding status within female social groups is discussed.

Heterozygous mutations of OTX2 cause severe ocular malformations

Major malformations of the human eye, including microphthalmia and anophthalmia, are examples of phenotypes that recur in families yet often show no clear Mendelian inheritance pattern. Defining loci by mapping is therefore rarely feasible. Using a candidate-gene approach, we have identified heterozygous coding-region changes in the homeobox gene OTX2 in eight families with ocular malformations. The expression pattern of OTX2 in human embryos is consistent with the eye phenotypes observed in the patients, which range from bilateral anophthalmia to retinal defects resembling Leber congenital amaurosis and pigmentary retinopathy. Magnetic resonance imaging scans revealed defects of the optic nerve, optic chiasm, and, in some cases, brain. In two families, the mutations appear to have occurred de novo in severely affected offspring, and, in two other families, the mutations have been inherited from a gonosomal mosaic parent. Data from these four families support a simple model in which OTX2 heterozygous loss-of-function mutations cause ocular malformations. Four additional families display complex inheritance patterns, suggesting that OTX2 mutations alone may not lead to consistent phenotypes. The high incidence of mosaicism and the reduced penetrance have implications for genetic counseling.

Taming anxiety in laboratory mice

Routine laboratory animal handling has profound effects on their anxiety and stress responses, but little is known about the impact of handling method. We found that picking up mice by the tail induced aversion and high anxiety, whereas use of tunnels or open hand led to voluntary approach, low anxiety and acceptance of physical restraint. Using the latter methods, one can minimize a widespread source of anxiety in laboratory mice.

The genetic basis of individual recognition signals in the mouse

The major histocompatibility complex (MHC) is widely assumed to be a primary determinant of individual-recognition scents in many vertebrates [1-6], but there has been no functional test of this in animals with normal levels of genetic variation. Mice have evolved another polygenic and highly polymorphic set of proteins for scent communication, the major urinary proteins (MUPs) [7-12], which may provide a more reliable identity signature ([13, 14] and A.L. Sherborne, M.D.T., S. Paterson, F.J., W.E.R.O., P. Stockley, R.J.B., and J.L.H., unpublished data). We used female preference for males that countermark competitor male scents [15-17] to test the ability of wild-derived mice to recognize individual males differing in MHC or MUP type on a variable genetic background. Differences in MHC type were not used for individual recognition. Instead, recognition depended on a difference in MUP type, regardless of other genetic differences between individuals. Recognition also required scent contact, consistent with detection of involatile components through the vomeronasal system [6, 18]. Other differences in individual scent stimulated investigation but did not result in individual recognition. Contrary to untested assumptions of a vertebrate-wide mechanism based largely on MHC variation, mice use a species-specific [12] individual identity signature that can be recognized reliably despite the complex internal and external factors that influence scents [2]. Specific signals for genetic identity recognition in other species now need to be investigated.

Urinary proteins and the modulation of chemical scents in mice and rats

The urine of mice, rats and some other rodents contains substantial quantities of proteins that are members of the lipocalin family. The proteins are thought to be responsible for the binding and release of low molecular weight pheromones, and there is now good evidence that they discharge this role, providing a slow release mechanism for volatile components of scent marks. However, the proteins may function as chemosignalling molecules in their own right, contributing one or more roles in the communication of individual identity and scent mark ownership. In this review, we summarize current understanding of the structure and function of these urinary proteins, and speculate about their role as supporters or as key participants in the elaboration of the complex chemosensory properties of a rodent scent mark.

The Genetic Basis of Inbreeding Avoidance in House Mice

Summary Animals might be able to use highly polymorphic genetic markers to recognize very close relatives and avoid inbreeding [1, 2]. The major histocompatibility complex (MHC) is thought to provide such a marker [1, 3–6] because it influences individual scent in a broad range of vertebrates [6–10]. However, direct evidence is very limited [1, 6, 10, 11]. In house mice (Mus musculus domesticus), the major urinary protein (MUP) gene cluster provides another highly polymorphic scent signal of genetic identity [8, 12–15] that could underlie kin recognition. We demonstrate that wild mice breeding freely in seminatural enclosures show no avoidance of mates with the same MHC genotype when genome-wide similarity is controlled. Instead, inbreeding avoidance is fully explained by a strong deficit in successful matings between mice sharing both MUP haplotypes. Single haplotype sharing is not a good guide to the identification of full sibs, and there was no evidence of behavioral imprinting on maternal MHC or MUP haplotypes. This study, the first to examine wild animals with normal variation in MHC, MUP, and genetic background, demonstrates that mice use self-referent matching of a species-specific [16, 17] polymorphic signal to avoid inbreeding. Recognition of close kin as unsuitable mates might be more variable across species than a generic vertebrate-wide ability to avoid inbreeding based on MHC.

Scent marks as reliable signals of the competitive ability of mates

The quality of an individuals odour can allow potential mates to discriminate against individuals of low social class, poor health status or unsuitable genotype. Competitive scent marking provides a further mechanism which could allow mates to discriminate between individuals of apparently high quality. The presence or absence of fresh countermarks from competitors within an owners territory or area marked by a dominant animal provides a reliable indicator of the owners ability to defend its territory or dominate competitors. This could be used by potential mates to discriminate between individuals advertising their apparently high competitive ability through their scent-marking behaviour and odour quality. We tested this by manipulating scent marks in the neighbouring territories of wild-caught male house mice, Mus domesticus. As predicted, oestrous females used scent marks to select males apparently able to defend exclusive territories over those unable to exclude intruders. Females were more strongly attracted to the odour of owners of exclusively marked territories and showed more sexually related behaviour when interacting with these males. Furthermore, while females preferred a territory containing a better protected nest site regardless of the owners apparent competitive ability, they still used the presence or absence of intruder countermarks when selecting a potential mate. This suggests that females use scent marks as a reliable signal of the best-quality mate among neighbouring males independently of their nest location. Since assessment depends on both the territory holders own marks and those of competitor males, countermarking is likely to be an important mechanism of competition for mates between neighbours. Copyright 1998 The Association for the Study of Animal Behaviour

Positional proteomics: selective recovery and analysis of N-terminal proteolytic peptides.

Bottom-up proteomics is the analysis of peptides derived from single proteins or protein mixtures, and because each protein generates tens of peptides, there is scope for controlled reduction in complexity. We report here a new strategy for selective isolation of the N-terminal peptides of a protein mixture, yielding positionally defined peptides. The method is tolerant of several fragmentation methods, and the databases that must be searched are substantially less complex.

Unravelling the chemical basis of competitive scent marking in house mice

Major urinary proteins (MUPs) in the urine of male house mice, Mus domesticus, bind the male signalling volatiles 2- sec -butyl-4,5-dihydrothiazole (thiazole) and 3,4-dehydro- exo -brevicomin (brevicomin) and slowly release these volatiles from urinary scent marks. To examine the role of urinary proteins and volatiles, either attached or unattached to the proteins, in competitive scent marking, we fractionated urine from isolated male BALB/c laboratory mice, Mus musculus, by size-exclusion chromatography into three pools. Pool I contained all of the urinary proteins and their bound ligands while pools II and III contained lower molecular weight components including unbound signalling volatiles. In experiment 1, pools I-III were streaked out on to absorbent paper (Benchkote) and introduced into enclosures housing single wild-caught male mice, together with a clean control surface. Each male was tested with fresh stimuli and with aged stimuli deposited 24 h previously. Only pool I stimulated significantly more countermarking and investigation than the control, attracting mice to investigate from a distance even when the rate of ligand release was considerably reduced after 24 h. Experiment 2 examined responses to pool I when this was fresh, aged by 7 days, or had been mixed with menadione to displace ligands from the proteins. Although all three protein stimuli were investigated and countermarked more than a clean control, the aged and menadione-treated pool I stimulated the strongest responses, despite containing the lowest levels of thiazole and brevicomin. Thus competitive countermarking is stimulated by proteins or by nonvolatile protein-ligand complexes in male urine, while release of volatile ligands attracts attention to a competitors scent marks. Copyright 1999 The Association for the Study of Animal Behaviour.

Female recognition and assessment of males through scent

Scents play key roles in mediating sexual behaviour in many vertebrates, both in the recognition of opposite sex conspecifics and in assessing the suitability of different individuals as potential mates. The recognition and assessment that underlies female attraction to male scents involves an important interaction between the main and accessory (vomeronasal) olfactory systems. Female mice gain information through the vomeronasal system on nasal contact with a scent source that is essential to stimulate attraction to an individual males scent. Three highly polymorphic multigene families contribute involatile proteins and peptides to mouse scents that are detected through specific vomeronasal receptors during contact with scent. Major urinary proteins (MUPs) provide an individual genetic identity signature that underlies individual recognition and assessment of male competitive ability, kin recognition to avoid inbreeding, and genetic heterozygosity assessment. Familiar mates are recognised in the context of pregnancy block using MHC peptides, while exocrine-gland secreting peptides (ESPs) are likely to play additional roles in sexual assessment. By associating this involatile information in individual male scents, gained on initial scent contact, with the individual males airborne volatile signature detected simultaneously through the main olfactory system, females subsequently recognise and are attracted by the individual males airborne volatile signature alone. This allows much more rapid recognition of scents from familiar animals without requiring physical contact or processing through the vomeronasal system. Nonetheless, key information that induces attraction to a males scent is held in involatile components detected through the vomeronasal system, allowing assessment of the genetic identity and attractiveness of each individual male.