Alternative approach for list of abbreviations

[joelostblom]

In addition to the current approach using ~~~~~ spacers, you can do the following (with \usepackage{longtable} in you header-includes):

\begin{longtable}[l]{l l}
    \textbf{AP} & Anterior-Posterior \\
    \textbf{PS} & Primitive Streak \\
    \textbf{mPSC} & mouse Pluripotent Stem Cell \\
\end{longtable}

Might make it a bit easier to read without those tildes, but I am not an expert on latex so can't guarantee that they are exactly equivalent although it look similar in the output.