Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death worldwide and an accelerating decline of lung function is the earliest and a major indicator of the onset of COPD. Therefore it has become necessary to understand the genetic basis of this complex physiological trait in order to determine the potential susceptibility factors of this disease. REINHARD et al (2005) performed the genome wide linkage analysis study with inbred mice having extremely divergent lung function (C3H/HeJ versus JF1/Msf) and identified multiple Quantitative Trait Loci (QTLs) on mouse chromosomes (mCh) 5, 15, 17, and 19 with Logarithm of odd (LOD) scores > or = 4. Significant linkages to total lung capacity (TLC) were detected on mCh 15 and 17, to dead space volume (VD) and lung compliance (C(L)) on mCh 5 and 15, to C(L) on mCh 19, and to diffusing capacity for CO (D(co)) on mCh 15 and 17. Several of the mouse chromosomal regions identified were syntenic to human chromosomal regions identified with linkage to FEV1 (forced expiratory volume-1 second), FVC (forced vital capacity), or FEV1/FVC in separate studies. Using a systematic approach of expression QTL (e-QTL) strategy and exon-wise sequencing of suggested candidate genes followed by predicted protein structure and property, GANGULY et al (2007) recently proposed four candidate genes for lung function in mice. They are superoxide dismutase 3, extracellular [SOD3; mCh 5: V(D)], trefoil factor 2 (TFF2; mCh 17: TLC and D(co)), ectonucleotide pyrophosphatase/phosphodiesterase 2 (ENPP2; mCh 15:TLC and C(L)), and relaxin 1 (RLN1; mCh 19; CL and CL/TLC). As a part of functional validation, gene-targeted Sod3-/- mice were detected with increased conducting airway volume (V(D)/TLC) compared with strain-matched control Sod3+/+ mice, consistent with the QTL on mCh 5. Findings with gene-targeted mice suggested that SOD3 is a contributing factor defining the complex trait of conducting airway volume. The human variation in these genes needs further study both in lung development and in the development of lung disease as a part of translational approach.