Murine dorsal hair type is genetically determined by polymorphisms in candidate genes that influence BMP and WNT signalling.

Mouse dorsal coat hair types, guard, awl, auchene and zigzag, develop in three consecutive waves. To date, it is unclear if these hair types are determined genetically through expression of specific factors or can change based on their mesenchymal environment. We undertook a novel approach to this question by studying individual hair type in 67 Collaborative Cross (CC) mouse lines and found significant variation in the proportion of each type between strains. Variation in the proportion of zigzag, awl and auchene, but not guard hair, was largely due to germline genetic variation. We utilised this variation to map a quantitative trait locus (QTL) on chromosome 12 that appears to influence a decision point switch controlling the propensity for either second (awl and auchene) or third wave (zigzag) hairs to develop. This locus contains two strong candidates, Sostdc1 and Twist1, each of which carry several ENCODE regulatory variants, specific to the causal allele, that can influence gene expression, are expressed in the developing hair follicle, and have been previously reported to be involved in regulating human and murine hair behaviour, but not hair subtype determination. Both of these genes are likely to play a part in hair type determination via regulation of BMP and/or WNT signalling.

A review of sonographic thyroid volume and iodine sufficiency in children: An Australian perspective.

Sonographic measurement of the thyroid gland volume is a safe and reliable method for epidemiologic studies in iodine deficiency disorders. Several factors such as age, sex and anthropometric characteristics are known to be the determinants of thyroid gland size but the most widely studied is the effect of insufficient iodine intake. Low iodine intake induces enlargement of the thyroid gland known as goitre. The assessment of urinary iodine concentration alone is not reliable as it can vary daily within individuals. Urinary iodine concentration in conjunction with sonographic thyroid gland measurements is a widely used method of thyroid gland assessment. Establishment of normative thyroid volume is essential for the assessment of iodine deficiency disorders, and studies have been conducted in several countries. These studies have shown that thyroid gland volumes are likely population-specific even in iodine-sufficient countries limiting the effectiveness of international reference ranges. Based on currently available data of sonographic thyroid gland volume measurements and how they vary across populations of school children, this review argues for the establishment of population-specific reference ranges in regions such as Australia, which are now considered iodine-sufficient.