UICONTROLs do not support TeX or LaTeX symbols.
To work around this limitation, one can use a TEXT object which does support LaTeX. Note that the TEXT object is not accessible in GUIDE though. Therefore you can use the following piece of code in your figure's OpeningFcn to automatically replace certain Static Text UICONTROLs with TEXT objects:
% TEXT annotations need an axes as parent so create an invisible axes which
% is as big as the figure
handles.laxis = axes('parent',hObject,'units','normalized','position',[0 0 1 1],'visible','off');
% Find all static text UICONTROLS whose 'Tag' starts with latex_
lbls = findobj(hObject,'-regexp','tag','latex_*');
for i=1:length(lbls)
l = lbls(i);
% Get current text, position and tag
set(l,'units','normalized');
s = get(l,'string');
p = get(l,'position');
t = get(l,'tag');
% Remove the UICONTROL
delete(l);
% Replace it with a TEXT object
handles.(t) = text(p(1),p(2),s,'interpreter','latex');
end
Place this piece of code right before the following line in the OpeningFcn:
% Update handles structure
guidata(hObject, handles);
Further in GUIDE give the Static Text boxes which need to be rendered using LaTeX, a 'Tag' which starts with latex_.
