Team:SUSTech Shenzhen/Neuron Network Model

Neuron Network

Model

This model is built to select neurons which may have signal connections with AWA and AWB and to determine the specific promoters to express gene in them.

After we successfully integrated ord-10::CoChR::GEM-GECO::mCherry and str-1::Chrimson::GEM-GECO::GFP fusion genes in C. elegans(Caenorhabditis elegans) respectively, we can train worms by stimulating neurons AWA and AWB. After that, we hope to focus on the neuron network change due to new learning behaviors.

To achieve that, GEM-GECO, as calcium indicator, will also express in the downstream neurons of AWA AWB. We use our optical platform to receive the output signal of GEM-GECO when the neurons are activated. We expect to witness that for example, after worms are trained to be addicted with alcohol, the neuronal activation pattern surrounding the AWA AWB neuron will also change. New signal connection pathway may be built among neurons.

Firstly, we assume that the strength of a connection is positively correlated with the number of synapses, including synaptic outputs from any group of presynaptic neurons in the network should represent more than 10% of the total synaptic outputs of the presynaptic neurons and synaptic inputs to any group of postsynaptic neurons in the network should represent more than 10% of the synaptic inputs of the postsynaptic neurons.

2 steps are considered to design the further experiment:

1. Select the neurons that are strongly connected with AWA AWB.
2. Select specific promoters to express GEM-GECO in the neurons.

Fig.1 The purpose of this model is to select promoters used in neurons which have greatest probability to be lighted on when AWA and AWB are active.

Determining the Connection Strength among Neurons

Firstly, we assume that the strength of a connection between neurons is positively correlated with the number of synapses. It includes synaptic outputs from any group of presynaptic neurons in the network should represent more than 10% of the total synaptic outputs of the presynaptic neurons and synaptic inputs to any group of postsynaptic neurons in the network should represent more than 10% of the synaptic inputs of the postsynaptic neurons(Figure 2.).

Figure 2. Diagram of a connection between neurons based on first assumption.

Determining the Promoters

After getting a collection of potential downstream neurons, we need to determine which promoter to use. There are the basic requirements:

1. The selected neurons cannot be too closed to each other. Thus we can distinguish each of them under microscope.
2. AIA, AIY, AVA are the three neurons indicated to play important roles in worms movement [1,2,3], so they are prior to choose.
3. The selected promoters should be as few as possible to express in neurons as many as possible.

Here are the work flow:

1.Make a table recording the promoter expression location. Data source. The table contains 43 neurons and their promoters

Table 1 The table contains 43 neurons and their promoters, promoters are in the first line. Their correlated promoters are shown in one column.

2.Make a table recording the neurons that cannot use the same promoter for they are close to each other. Data source. The table is manually made by evaluating the difficulty to distinguish neurons based on the online 3D model of C. elegans’ neurons (Figure 2.)

Table2 The table of neurons can not be distinguished ( shown in one column).

3.Write a MATLAB program to search the appropriate promoters based on the table2 and the requirement above 4.Remove the negative result based on table2 (in one column).

Figure 3. Diagram of a connection among neurons surrounding AWA and AWB neurons The red number shows the count of synapses between 2 neurons

5.Print result in a text

Result:

According to our preference of neuron AIA,AIY,AVA, we selected two promoters: cho-1, unc-8.

cho-1 is expressed in AIA, AIY, VB

unc-8 is expressed in ASH, AVB, VB, AVA

Figure 4. A)3D model of AIA, AIY, VB’s positions in C. elegans.

Figure 5. 3D model of ASH, AVB, VB, AVA’s positions in C. elegans

Further work

We have constructed plasmids cho-1::GEM-GECO::GFP and unc-8::GEM-GECO::GFP. In the near future, we will demonstrate whether the neuronal connection among these neurons will change after worms get the newly learned behaviors.

References

Made by from the elegans.Inc in SUSTech_Shenzhen.

Licensed under CC BY 4.0.

• ©2017 SUSTech_Shenzhen