Correlating gene expression with larval competence and the effect of age and parentage on metamorphosis in the tropical abalone Haliotis asinina

The non-geniculate crustose coralline alga (CCA) Mastophora pacifica can induce the metamorphosis of competent Haliotis asinina (Vetigastropoda) larvae. The ability to respond to this natural cue varies considerably with larval age, with a higher proportion of older larvae (e.g. 90 h) able to metamorphose in response to M. pacifica than younger larvae (e.g. 66 h). Here we document the variation in time to acquisition of competence within a larval age class. For example, after 18 h of exposure to M. pacifica, approximately 15 and 36% of 84 and 90-h-old H. asinina larvae had initiated metamorphosis, respectively. This age-dependent response to M. pacifica is also observed when different aged larvae are exposed to CCA for varying periods. A higher proportion of older larvae require shorter periods of exposure to CCA than younger larvae in order to initiate metamorphosis. In this experiment, as in the previous, a small proportion of young larvae were able to respond to brief periods of CCA exposure, suggesting that they had developed the same state of competency as the majority of their older counterparts. Comparisons of the proportions of larvae undergoing metamorphosis between families reveals that parentage also has a significant (P < 0.05) affect on whether an individual will initiate metamorphosis at a given age. These familial differences are more pronounced when younger, largely pre-competent larvae (i.e. 66 h old) are exposed to M. pacifica, with proportions of larvae undergoing metamorphosis differing by as much as 10 fold between families. As these data suggest that variation in the rate of development of the competent state has a genetic basis, and as a first step towards identifying the molecular basis to this variation, we have identified numerous genes that are differentially expressed later in larval development using a differential display approach. Spatial expression analysis of these genes suggests that they may be directly involved in the acquisition of competence, or may play a functional role in the postlarva following metamorphosis.

Using Inside-Outside Algorithm for Estimation of the Offspring Distribution in Multitype Branching Processes

Multitype branching processes (MTBP) model branching structures, where the nodes of the resulting tree are particles of different types. Usually such a process is not observable in the sense of the whole tree, but only as the “generation” at a given moment in time, which consists of the number of particles of every type. This requires an EM-type algorithm to obtain a maximum likelihood (ML) estimate of the parameters of the branching process. Using a version of the inside-outside algorithm for stochastic context-free grammars (SCFG), such an estimate could be obtained for the offspring distribution of the process.

A role for epigenetic modulation of the innate immune response during aging

The ageing process results from a complex interplay between genes and the environment that can precipitate an uncontrolled inflammation. Epigenetic changes are believed to provide a link between the environment and nutrition to gene expression by altering the activity of some histone-modifying protein. Epigenetic modifications of DNA and histone proteins have been proposed as important contributory mechanisms to the retention of metabolic memory over time. A thorough understanding of the posttranscriptional and epigenetic factors involved in both normal ageing and age-related disease may inform new strategies and approaches to diagnose, treat, or suppress many aspects of age-dependent frailty.

On the Extinction Probability for Bisexual Branching Processes in Varying Environments

2000 Mathematics Subject Classification: 60J80

Limit Theorems for Branching Processes with Random Migration Components

The classical Bienaymé-Galton-Watson (BGW) branching process can be interpreted as mathematical model of population dynamics when the members of an isolated population reproduce themselves independently of each other according to a stochastic law.

Em Estimation of the Offspring Distribution in Mutitype Branching Processes - a Model in Cell Kinetics

2000 Mathematics Subject Classification: 60J80, 60J85, 62P10, 92D25.

Subcritical Randomly Indexed Branching Processes

2000 Mathematics Subject Classification: 60J80, 62P05.

Robust Estimation in Multitype Branching Processes Based on their Asymptotic Properties

2000 Mathematics Subject Classification: 60J80.

Branching Stochastic Processes: Regulation, Regeneration, Estimation, Applications

2000 Mathematics Subject Classification: 60J80.

Offspring Mean Estimators in Branching Processes with Immigration

2000 Mathematics Subject Classification: 60J80.

On Y-Linked Genes and Bisexual Branching Processes

2000 Mathematics Subject Classification: 60J80.

Estimators in Branching Processes with Immigration

2000 Mathematics Subject Classi cation: 60J80.

A New Class of Processes for Formalizing and Generalizing Individual-Based Models: The Semi-Semi-Markov Processes

2000 Mathematics Subject Classification: 60K15, 60K20, 60G20,60J75, 60J80, 60J85, 60-08, 90B15.

A Note on the Extinction Problem for Controlled Multitype Branching Processes

2000 Mathematics Subject Classification: 60J80, 60J10.

Extremes of Bivariate Geometric Variables with Application to Bisexual Branching Processes

2000 Mathematics Subject Classification: 60J80, 60G70.