Atrial fibrillation (AF), the most common cardiac arrhythmia, is a major contributor to population mortality and morbidity, particularly stroke-risk. 1 Atrialtissue fibrosis is a central pathophysiological feature and hampers AF-treatment; the underlying molecular mechanisms are poorly understood and present therapies are inadequate. 2 Here, we show that calcitonin (CT), a well-recognized hormone product of the thyroid gland involved in bone metabolism, 3 is produced in significant quantities by atrial cardiomyocytes and acts in a paracrine fashion on neighbouring collagenproducing fibroblasts to control their proliferation and secretion of extracellular matrix proteins. Global disruption of CT-receptor signalling in mice causes atrial fibrosis and increases AF susceptibility. Atrial-specific knockdown (KD) of CT in atrial-targeted liver-kinase B1 (LKB1)-KD mice promotes atrial fibrosis and prolongs/increases the number of spontaneous AF-episodes, while atrial-specific CT overexpression prevents fibrosis and AF in LKB1-KD mice. Patients with persistent AF are characterised by six-

Glycosylated hemoglobin (HbA1c) determination is a powerful means for assessing the evaluation and management of patients with diabetes mellitus. Hemoglobin (Hb) variants and chemically modified derivatives of Hb can affect the accuracy of measurement of HbA1c done by various analytical methods. We report a patient with a rare variant of Hb (Hb Hope) that caused an abnormally high value of HBA1c when assayed using immunoturbidimetric assay ("Tina-quant" 2nd generation assay) and also elucidate the nature of the variant.

Unique Molecular Identifiers (UMIs) are random oligonucleotide sequences that remove PCR amplification biases. However, the impact that PCR associated sequencing errors have on the accuracy of generating absolute counts of RNA molecules is underappreciated. We show that PCR errors are the main source of inaccuracy in both bulk and single-cell sequencing data, and synthesizing UMIs using homotrimeric nucleotide blocks provides an error correcting solution, that allows absolute counting of sequenced molecules.