Mathematical Biology Seminar: Jesus Espinal

  • Date: 04/26/2011
  • Time: 14:00
Jesus Espinal (UNAM, Mexico)

University of British Columbia


Discrete Dynamics Model for the Speract-Activated Ca2+ Signaling Network Relevant to Sperm Motility.


A crucial element for life is fertilization and for this to take place a
sperm must meet an egg. The question is how does the sperm locate and
swim towards the egg. Here, we consider the case of sea urchins for
which fertilization is external and communication between egg and sperm
is achieved by means of molecules secreted by the egg, that diffuse to
the sperm. Once they reach the sperm they attach to its flagellum and
trigger a biochemical signaling pathway that produces oscillations in
the internal calcium concentration. These fluctuations are known to
reorient the sperm navigation. Our main concern is to increase our
understanding of this activation process. We achieve this by means of a
network model with linked nodes representing the pathway elements and
their interactions. In our approach nodes take discrete values and time
evolution is dictated by regulatory tables. With this logical network we
have been able to identify unforeseen elements for the regulation of
the onset and periodicity of the calcium oscillations, which we have
corroborated experimentally. These time evolution characteristics affect
sperm navigation properties such as the presence or absence of
chemotaxis. Our study also reveals that the network dynamics operates in
a critical regime, this meaning that it strikes a balance between
evolvability and robustness, a condition that favors the adaptation to
different environments and that has probably been achieved throughout
evolution. Our work hence provides a new instance for the proposition
that life takes place at criticality.

Other Information: 

Location: WMAX 110


For more information please visit UBC Mathematical Biology department