{'fraction_non_alphanumeric': 0.01819560272934041, 'fraction_numerical': 0.00530705079605762, 'mean_word_length': 5.633165829145729, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Heterochromatin is retained during lens fiber cell differentiation

The lens of the eye contains both epithelial and fiber cells, with fibers cells deriving from the equatorial epithelium. When these cells differentiate, the nucleus and cellular organelles are broken down to facilitate transparency. However, small fragments of DNA can remain in fully mature lens fiber cells, although their structure is unknown. We found that histone H3, trimethylated on Lysine 9, as well as 5‐Methylcytosine, which are both associated with compact heterochromatin, co‐localize with these DNA fragments. In contrast, the DNA remnants are not associated with either histone H3 Lysine 9 acetylation or histone H4 lysine 8 acetylation, which are predominant in the more accessible euchromatin. This data suggests that the DNA fragments persisting in mature lens fiber cells are entirely composed of heterochromatin, likely because their highly compacted state prevented access of the nucleases responsible for DNA degradation during lens fiber cell differentiation. This led to the further hypothesis, which is currently being tested, that these fragments predominantly contain transcriptionally silent genes, which are likely to be found in heterochromatin. Supported by Howard Hughes Medical Institute and the National Eye Institute.