The long noncoding RNAHand2asorchestrates heart development through regulation of precise expression ofHAND2

Abstract

1Rigorous exploration and dissection of potential actions and effects of long noncoding RNA 2 (lncRNA) in animals remain challenging. Here using multiple knockout mouse models and single-alleles of Hand2as in mouse (Han et al., 2018). Full-length deletion of the entire Hand2as sequence 1 (Hand2as F/F KO) led to dysregulated cardiac gene expression programs, ventricular septal defects 2 and heart hypoplasia and perinatal death, reminiscent of congenital heart diseases. A short distal 3 deletion at the 3' end of the Hand2as locus (Hand2as D/D KO) caused severe contraction defects in 4 adult heart that progressively worsened with increasing age. In comparison, short deletion of the 5' 5 promoter and exons of Hand2as (Hand2as P/P KO) effectively diminished Hand2as expression, but 6 failed to produce discernable heart phenotypes in either embryos or adults. These results indicate that 7 the Hand2as DNA locus, rather than its transcription/transcripts, primarily controls heart 8 development and function. To our surprise, cardiac expression of HAND2 was sustained in all three 9 Hand2as KO mouse models we generated, in sharp contrast to the abolished expression of HAND2 10 in the Uph/Hand2as polyA KI embryos (Anderson et al., 2016). Importantly, single-cell 11 transcriptomic analysis revealed subtle yet prevalent upregulation of HAND2 and concordant global 12 gene expression changes in subsets of cardiac cells of Hand2as F/F embryos lacking the entire Hand2as 13 DNA sequence. Altogether, these results illustrate a fine-tuning yet critical role for the lncRNA 14 Hand2as locus in restricting the precise, spatial expression of HAND2, through which Hand2as 15 modulates cardiac lineage development and heart function. This study reveals the unexpected 16 complexity of lncRNA function in vivo, and also emphasize the usage of complementary genetic and 17 single-cell approaches to delineate the primary molecular effects and elucidate physiological 18 functions of an lncRNA in animals.

Comprehensive Overview of Non-coding RNAs in Cardiac Development

“…Finally, the expression of HAND2 -critical for ventricular CMs expansion -is initially discovered in the cardiac crescent at E7.75 and will continue throughout the linear heart tube at E8.5. It has been recently shown that the lncRNA Uph (also named Hand2as or lncHand2), playing critical roles in the regulation of the precise expression of HAND2, together with miR-1-2 family in looping heart, to eventually lead to chamber formation [56,57].…”