*2.2. ABCA7 Alternative Splicing*

There are two isoforms of ABCA7, arising as a result of alternative splicing, both of which are detected in the human brain [21,25]. The splicing variant is named Type II ABCA7 and gives a protein with 28 amino acids in the N terminal tail instead of the 166 amino acids present in the full-length ABCA7. These variants show a tissue-dependent expression pattern and differential cellular sub-localization. While full length ABCA7 has been detected on the cell surface and intracellularly, the so-called Type II ABCA7 splice variant is only detected in the endoplasmic reticulum [21]. Northern blot analysis performed with human tissue samples showed that Type II ABCA7 is abundant in lymph node, spleen, thymus and trachea whereas full ABCA7 is strongly expressed in brain and bone marrow [21]. Thus, it is possible that these variant proteins have different biological functions.
