Fusome topology and inheritance during insect gametogenesis
Fig 3
A model for fusome growth and inheritance during oogenesis.
A) Starting with a spectrosome of volume v0 and fusome plug at the first division of volume v1, the volume fraction f1,2 of the 2-cell female cyst can be represented as shown in Eq 1, where the volume fraction in cell 1 at this stage is α and the asymmetry in sharing of the newly formed fusome component between mother and daughter cell is β. B) At the 2-to-4-cell transition, two new fusome plugs are added in the same manner as in A, with each contributing volume v2. C) Divisions occur again to form 8- and 16-cell cysts, where the total fusome volume can be tracked throughout cyst formation, and expressions for volume fractions of fusome within each cell at each cyst size to be derived. D) Error calculations for ranges of the model parameters α and β. For each set of parameters, model volume fractions for each cyst size were calculated and compared with measured data by summing over the squared residuals between measured and derived volume fractions over each cell at all cyst sizes. The minimum error using this metric was found at the value α = 0.700, β = 0.515, corresponding to a scenario where fusome plugs are added evenly between the mother and daughter cells at each successive division. Explanation of model assumptions and equations can be found in the Materials and Methods. Comparison with measured data can be found in S1 Fig.