\begin{tikzpicture}[ node distance=2cm]
\node[MyNode, label=left:$4$] (A) {};
\nodeMyNode, label=left:$1$[above of=A] {};
\nodeMyNode, label=right:$2$[right of=B] {};
\nodeMyNode, label=right:$3$[below of=C] {};
\draw [middlearrow={>}] (B) -- (C);
\draw [middlearrow={>}] (A) -- (D);
\draw [middlearrow={>}] (A) -- (B);
\draw [middlearrow={>}] (D) -- (C);
\end{tikzpicture}
