UserTutorials/CreatingAndUsingANewCellMutationState

This tutorial is automatically generated from the file trunk/cell_based/test/tutorial/TestCreatingAndUsingANewCellMutationStateTutorial.hpp at revision r12669. Note that the code is given in full at the bottom of the page.

An example showing how to create a new cell mutation state and use it in a cell-based simulation

Introduction

In the tumour spheroid tutorial we noted that a cell mutation state is always required when constructing a cell. In this tutorial, we show how to create a new cell mutation state class, and how this can be used in a cell-based simulation.

1. Including header files

As in previous cell-based Chaste tutorials, we begin by including the necessary header file and archiving headers.

#include <cxxtest/TestSuite.h>
#include <boost/archive/text_oarchive.hpp>
#include <boost/archive/text_iarchive.hpp>

The next header defines a base class for cell mutation states. Our new cell mutation state will inherit from this abstract class.

#include "AbstractCellMutationState.hpp"

The remaining header files define classes that will be used in the cell population simulation test. We have encountered each of these header files in previous cell-based Chaste tutorials.

#include "HoneycombMeshGenerator.hpp"
#include "WildTypeCellMutationState.hpp"
#include "FixedDurationGenerationBasedCellCycleModel.hpp"
#include "GeneralisedLinearSpringForce.hpp"
#include "CellBasedSimulation.hpp"
#include "CellsGenerator.hpp"

Defining the cell mutation state class

As an example, let us consider a cell mutation state representing the p53 172R-H gain-of-function mutant, which is equivalent to the common 175R-H human breast cancer mutant; for further details on this mutant, see for example Murphy et al, FASEB J. 14:2291-2302 (2000).

Wild-type p53 has been referred to as the "guardian of the genome", responding to DNA damage or checkpoint failure by either arresting cell cycle progression to facilitate DNA repair or initiating an apoptotic pathway to remove damaged cells. Approximately 40% of human breast cancers contain alterations in p53.

As we can see, apart from a serialize() method and a constructor, this class does not contain any member variables or methods. This is because generally a cell's mutation state is used, much like a flag, by other classes when determining a cell's behaviour (whether a cell should undergo apoptosis following prolonged stress, for example, or alter its proliferative behaviour).

class P53GainOfFunctionCellMutationState : public AbstractCellMutationState
{
private:
    friend class boost::serialization::access;
    template<class Archive>
    void serialize(Archive & archive, const unsigned int version)
    {
        archive & boost::serialization::base_object<AbstractCellMutationState>(*this);
    }
public:

The only public method is a default constructor, which just calls the base constructor with a single unsigned parameter. This sets the value of the base class member variable mColour, which can be used by visualization tools to paint cells with this mutation state a distinct colour if required.

    P53GainOfFunctionCellMutationState()
        : AbstractCellMutationState(5)
    {
    }
};

As mentioned in previous cell-based Chaste tutorials, we need to include the next block of code to be able to archive the cell mutation state object in a cell-based simulation, and to obtain a unique identifier for our new cell mutation state for writing results to file.

#include "SerializationExportWrapper.hpp"
CHASTE_CLASS_EXPORT(P53GainOfFunctionCellMutationState)
#include "SerializationExportWrapperForCpp.hpp"
CHASTE_CLASS_EXPORT(P53GainOfFunctionCellMutationState)

This completes the code for P53GainOfFunctionCellMutationState. Note that usually this code would be separated out into a separate declaration in a .hpp file and definition in a .cpp file.

The Tests

We now define the test class, which inherits from CxxTest::TestSuite.

class TestCreatingAndUsingANewCellMutationStateTutorial : public CxxTest::TestSuite
{
public:

Testing the cell mutation state

We begin by testing that our new cell mutation state is implemented correctly.

    void TestP53GainOfFunctionCellMutationState() throw(Exception)
    {

We begin by testing that some of the base class methods work correctly. We typically use shared pointers to create and access cell mutation states, as follows. This is because it makes sense for all cells that have the same mutation to share a pointer to the same cell mutation state object (although strictly speaking, they are not required to).

        boost::shared_ptr<AbstractCellMutationState> p_state(new P53GainOfFunctionCellMutationState);

Each cell mutation state has a member variable, mCellCount, which stores the number of cells with this mutation state. In fact, mCellCount is defined in the class AbstractCellProperty, from which AbstractCellMutationState inherits, as well as other cell properties such as CellLabel. We can test whether mCellCount is being updated correctly by our cell mutation state, as follows.

        TS_ASSERT_EQUALS(p_state->GetCellCount(), 0u);
        p_state->IncrementCellCount();
        TS_ASSERT_EQUALS(p_state->GetCellCount(), 1u);
        p_state->DecrementCellCount();
        TS_ASSERT_EQUALS(p_state->GetCellCount(), 0u);
        TS_ASSERT_THROWS_THIS(p_state->DecrementCellCount(),
                "Cannot decrement cell count: no cells have this cell property");

We can also test that mColour has been set correctly by our constructor, as follows.

        TS_ASSERT_EQUALS(p_state->GetColour(), 5u);

We can also test whether our cell mutation state is of a given type, as follows.

        TS_ASSERT_EQUALS(p_state->IsType<WildTypeCellMutationState>(), false);
        TS_ASSERT_EQUALS(p_state->IsType<P53GainOfFunctionCellMutationState>(), true);

We can also test that archiving is implemented correctly for our cell mutation state, as follows (further details on how to implement and test archiving can be found on the BoostSerialization? page).

        OutputFileHandler handler("archive", false);
        std::string archive_filename = handler.GetOutputDirectoryFullPath() + "mutation.arch";
        {
            AbstractCellProperty* const p_const_state = new P53GainOfFunctionCellMutationState();
            p_const_state->IncrementCellCount();
            TS_ASSERT_EQUALS(p_const_state->GetCellCount(), 1u);
            TS_ASSERT_EQUALS(dynamic_cast<AbstractCellMutationState*>(p_const_state)->GetColour(), 5u);
            std::ofstream ofs(archive_filename.c_str());
            boost::archive::text_oarchive output_arch(ofs);
            output_arch << p_const_state;
            delete p_const_state;
        }
        {
            AbstractCellProperty* p_state;
            std::ifstream ifs(archive_filename.c_str());
            boost::archive::text_iarchive input_arch(ifs);
            input_arch >> p_state;
            TS_ASSERT_EQUALS(p_state->GetCellCount(), 1u);
            P53GainOfFunctionCellMutationState* p_real_state = dynamic_cast<P53GainOfFunctionCellMutationState*>(p_state);
            TS_ASSERT(p_real_state != NULL);
            TS_ASSERT_EQUALS(p_real_state->GetColour(), 5u);
            delete p_state;
        }
    }

Using the cell mutation state in a cell-based simulation

We conclude with a brief test demonstrating how P53GainOfFunctionCellMutationState can be used in a cell-based simulation.

    void TestCellBasedSimulationWithP53GainOfFunctionCellMutationState() throw(Exception)
    {

The first thing to do, as before, is to set up the start time.

        SimulationTime::Instance()->SetStartTime(0.0);

We use the HoneycombMeshGenerator to create a honeycomb mesh covering a circular domain of given radius, as follows.

        HoneycombMeshGenerator generator(10, 10, 0);
        MutableMesh<2,2>* p_mesh = generator.GetCircularMesh(5);

We now create a shared pointer to our new cell mutation state, as follows.

        boost::shared_ptr<AbstractCellMutationState> p_state(new P53GainOfFunctionCellMutationState);

Next, we create some cells, as follows.

        std::vector<CellPtr> cells;
        CellsGenerator<FixedDurationGenerationBasedCellCycleModel, 2> cells_generator;
        cells_generator.GenerateBasicRandom(cells, p_mesh->GetNumNodes());

Now that we have defined the mesh and cells, we can define the cell population. The constructor takes in the mesh and the cells vector.

        MeshBasedCellPopulation<2> cell_population(*p_mesh, cells);

We then pass in the cell population into a CellBasedSimulation, and set the output directory and end time.

        CellBasedSimulation<2> simulator(cell_population);
        simulator.SetOutputDirectory("TestCellBasedSimulationWithp_motile");
        simulator.SetEndTime(10.0);

We create a force law and pass it to the CellBasedSimulation.

        GeneralisedLinearSpringForce<2> linear_force;
        linear_force.SetCutOffLength(3);
        simulator.AddForce(&linear_force);

Test that the Solve() method does not throw any exceptions.

        TS_ASSERT_THROWS_NOTHING(simulator.Solve());

Finally, we call Destroy() on the singleton classes.

        SimulationTime::Destroy();
        RandomNumberGenerator::Destroy();
    }
};

Code

The full code is given below

File name `TestCreatingAndUsingANewCellMutationStateTutorial.hpp`

#include <cxxtest/TestSuite.h>

#include <boost/archive/text_oarchive.hpp>
#include <boost/archive/text_iarchive.hpp>

#include "AbstractCellMutationState.hpp"
#include "HoneycombMeshGenerator.hpp"
#include "WildTypeCellMutationState.hpp"
#include "FixedDurationGenerationBasedCellCycleModel.hpp"
#include "GeneralisedLinearSpringForce.hpp"
#include "CellBasedSimulation.hpp"
#include "CellsGenerator.hpp"

class P53GainOfFunctionCellMutationState : public AbstractCellMutationState
{
private:

    friend class boost::serialization::access;
    template<class Archive>
    void serialize(Archive & archive, const unsigned int version)
    {
        archive & boost::serialization::base_object<AbstractCellMutationState>(*this);
    }

public:
    P53GainOfFunctionCellMutationState()
        : AbstractCellMutationState(5)
    {
    }
};

#include "SerializationExportWrapper.hpp"
CHASTE_CLASS_EXPORT(P53GainOfFunctionCellMutationState)
#include "SerializationExportWrapperForCpp.hpp"
CHASTE_CLASS_EXPORT(P53GainOfFunctionCellMutationState)

class TestCreatingAndUsingANewCellMutationStateTutorial : public CxxTest::TestSuite
{
public:

    void TestP53GainOfFunctionCellMutationState() throw(Exception)
    {
        boost::shared_ptr<AbstractCellMutationState> p_state(new P53GainOfFunctionCellMutationState);

        TS_ASSERT_EQUALS(p_state->GetCellCount(), 0u);
        p_state->IncrementCellCount();
        TS_ASSERT_EQUALS(p_state->GetCellCount(), 1u);
        p_state->DecrementCellCount();
        TS_ASSERT_EQUALS(p_state->GetCellCount(), 0u);
        TS_ASSERT_THROWS_THIS(p_state->DecrementCellCount(),
                "Cannot decrement cell count: no cells have this cell property");

        TS_ASSERT_EQUALS(p_state->GetColour(), 5u);

        TS_ASSERT_EQUALS(p_state->IsType<WildTypeCellMutationState>(), false);
        TS_ASSERT_EQUALS(p_state->IsType<P53GainOfFunctionCellMutationState>(), true);

        OutputFileHandler handler("archive", false);
        std::string archive_filename = handler.GetOutputDirectoryFullPath() + "mutation.arch";

        {
            AbstractCellProperty* const p_const_state = new P53GainOfFunctionCellMutationState();
            p_const_state->IncrementCellCount();

            TS_ASSERT_EQUALS(p_const_state->GetCellCount(), 1u);
            TS_ASSERT_EQUALS(dynamic_cast<AbstractCellMutationState*>(p_const_state)->GetColour(), 5u);

            std::ofstream ofs(archive_filename.c_str());
            boost::archive::text_oarchive output_arch(ofs);

            output_arch << p_const_state;

            delete p_const_state;
        }

        {
            AbstractCellProperty* p_state;

            std::ifstream ifs(archive_filename.c_str());
            boost::archive::text_iarchive input_arch(ifs);

            input_arch >> p_state;

            TS_ASSERT_EQUALS(p_state->GetCellCount(), 1u);

            P53GainOfFunctionCellMutationState* p_real_state = dynamic_cast<P53GainOfFunctionCellMutationState*>(p_state);
            TS_ASSERT(p_real_state != NULL);
            TS_ASSERT_EQUALS(p_real_state->GetColour(), 5u);

            delete p_state;
        }
    }

    void TestCellBasedSimulationWithP53GainOfFunctionCellMutationState() throw(Exception)
    {
        SimulationTime::Instance()->SetStartTime(0.0);

        HoneycombMeshGenerator generator(10, 10, 0);
        MutableMesh<2,2>* p_mesh = generator.GetCircularMesh(5);

        boost::shared_ptr<AbstractCellMutationState> p_state(new P53GainOfFunctionCellMutationState);

        std::vector<CellPtr> cells;
        CellsGenerator<FixedDurationGenerationBasedCellCycleModel, 2> cells_generator;
        cells_generator.GenerateBasicRandom(cells, p_mesh->GetNumNodes());

        MeshBasedCellPopulation<2> cell_population(*p_mesh, cells);

        CellBasedSimulation<2> simulator(cell_population);
        simulator.SetOutputDirectory("TestCellBasedSimulationWithp_motile");
        simulator.SetEndTime(10.0);

        GeneralisedLinearSpringForce<2> linear_force;
        linear_force.SetCutOffLength(3);
        simulator.AddForce(&linear_force);

        TS_ASSERT_THROWS_NOTHING(simulator.Solve());

        SimulationTime::Destroy();
        RandomNumberGenerator::Destroy();
    }
};